EIP 545A Microwave Counter: Option 04, a dead eprom, and a noisy fan

Another one of the EIP 545A counters, that are for some reason very frequently seen at my workshop. The reason for this instrument being here on the bench is simply for the fact that I found it on ebay, for a very reasonable price, non-working, but with the 04 OCXO option.

The option 04 provides 10^-9 level frequency stability, per day.

The actual OCXO unit is an Ovenaire 49-38c model 10 MHz oscillator. Very similar OCXOs are used in various HP equipment of the time.

The first item to fix – the very noisy fan. An ETRI model 126-LF-182. Fortunately, a very common 115 V model.

Replacing fans, you can’t just go for the flow rating, but you also need to consider flow direction, static pressure (mostly related to the blade shape and RPM), noise level, lifetime, and bearing type (ball bearing).

Found a very similar NMB fan, which is available from new production, at a reasonable price.

For comparison, the ETRI data put into the NMB pressure vs. flow characteristics, as red dots. Indeed, quite similar.

When changing the cable, from the old to the new fan (EIP uses a special connector, so I needed to re-use the old connector) – seems EIP didn’t trust their crimping, the cable was additionally soldered to the crimp pin.

The new fan installed, make sure to use some insulation tubing (not present in all EIP counters, but was present in this one, and a good idea, because the fan cable runs directly underneath the top cover, and over time, could be damage and expose mains voltage to the case (not a good thing!).

Next fix – a broken tantalum on the front panel (capacitor was OK, but one wire broken off) – fortunately, it could be soldered from the top, because disassembling the from panel is quite a time consuming task.

Finally, all these things fixed, but still a non-working EIP. It would not even count low frequency, or show any reaction on the display. All voltages OK. That’s strange – most likely something with the CPU, data bus, or similar. So, swapped the main CPU/control board with a know-good assembly, and the EIP came back to life. After some checking and probing, found one EPROM that had corrupted data – no wonder it didn’t start up.

While cleaning the power supply (removed the card from the main board), another issue showed up: EIP didn’t use sufficient thermal grease to make good contact of the assembly cage (used as a heat sink), and the heat conductor of the power supply assembly. All screws were tight, but no contact.

So I cleaned up everything, and added some more generous amounts of a good thermal compound.

This is the top view: you can see the OCXO auxiliary power supply to the left, and the OCXO in the right upper corner.

Also quite interesting, this unit has seen some pretty famous owners, including, Bell Labs, AmerSatCo, and Verestar, Inc. – probably, it has seen good use, also judging from the noise fan, which has 50 khours+ lifetime.

One all had been fixed and confirmed running, I could not resist to also add the 02 option Power Meter Upgrade to this unit, it is in the end just few eproms, and some additional parts for the A107 assembly.

… counting at 10 GHz, and showing the power.

EIP 545A Microwave Counter: El Salvador’s brittle leg disease

One more EIP 545A made it to my workshop, all in good shape, but not counting any microwaves, or other signals. The “gate” LED stays on permanently, and no counting also with the test function 01, which directs a 200 MHz signal to the counter chain.

Looking at the schematics (fortunately, there is a full service manual available), the issue needs to be with the A107 gate generator assy. And, easy find, no 100 kHz signal present. So something must be wrong with the 10 MHz to 100 kHz divider. Soldered a wire to some of the signal points, and needed to go all the way back to pin 1 of the 1st divider, which is a decade counter. No signal present.

The EIP 545A has all-socketed ICs, so pulled the IC from the socket, and 1 leg missing! The leg number 1 that needs to take the 10 MHz and put it into the silicon chip. Temporarily soldered a wire onto the IC, and it solves the issue, but not a good permanent solution.

Also the other pins are very brittle, when you touch them, and bend a little bit, they break off, rather than bend. This is quite common for some old Texas Instrument TTL chips, not quite sure way – maybe some precipitation hardening of the copper material they used, or an interaction of the copper core with the tin/lead top layer. We don’t know, but it seems to be particularly common with El Salvador’s chips.

Here, a close-up of an (intentionally) broken leg.

Also the LS175 on the same board, although it was all good electrically, shows quite severe brittleness. I replaced with right away (with a 1977 date coded LS175, also from Texas Instruments!).

The LS490, unfortunately, none to be found in my basement storage of all kinds of electronics parts. Many counter TTLs, but no 490. An the offers, they are pretty pricey, and I want this instrument to be fixed today, rather than waiting days for some overprices NOS TTL ICs to be delivered.

Looking at the datasheet, and schematic, it is a simple :10 divider, there are many of these – including the much more common LS390, and the pin arrangement is almost identical.

We only need to route the output of the 1st divider (a :2 divider) to the input of the next stage – and the LS390 will work like a LS490. The red lines show the additional connection needed (you need to bend up the pins, because they are grounded on the EIP A107 board).

…A107 board with the LS390 installed.

With these fixes, the 100 kHz signal came back! And the gate LED flashing!!

Tested with the test function 01 for some hours, and with some shaking and bending of the boards – just to be sure that the repair is permanent – all counting along fine. Also in band 3, no issues, and very good sensitivity all the way up to 18 GHz.

The last thing to do to before the unit will leave the workshop – adjusted the TCXO to the right frequency, it was only off by a few Hz, after many years of aging.

Oil Temperature Measurement Ni50: several meters of very thin wire

This is a short post about a very complicated and difficult repair. The function of the device is simple, it is an oil thermometer, of an old Deutz Locomotive, based on a resistance thermometer. Nowadays, virtually all resistance thermometers use platinum elements, but at the time, nickel was preferred for some applications, because nickel has a higher temperature coefficient of its resistance, giving about 62 ohms increase, per 100 ohms at 0°C, vs. only about 38.5 ohms, for platinum.

Moreover, the device used is a 50 ohms Ni resistance thermometer (Ni50), which is even less common than 100 ohms (Ni100). To add to the difficulty, also the thermometer itself is faulty, the pointer missing, the front glass damaged. All a bit rusty.

That’s the formula to calculate the resistance at any temperature – this is what we need to get.

Now, we have several approaches to fix this.

(1) Put in an electronic meter, to show the temperature – don’t want to do it, because it doesn’t fit to the locomotive’s age, and probably will fail soon with all the noise, oil, moisture, and vibration.

(2) Use a modern Pt100 element with some extra resistance to get the readings approximately right – this could work, but the electro-mechanical resistance thermometer indicator uses a pretty large test current, about 20~30 mA, much more than the rating of current thin film Pt100 elements, and wire-wound Pt100 are very expensive, especially, the larger sizes.

(3) Buying a Ni50 element, or two Ni100 elements. I tried, good luck, maybe for EUR 1000 you can get a couple made by some specialized company, custom order.

Well, all these options can’t really work, so I decided to wind my own Ni50 elements. Fortunately, I had some Ni wire, 0.065 mm diameter, of a reputable supplier around in my workshop from another project (has been there for about 20 years!), so let’s give it a try.

Some calculation quickly shows that a single layer or wire will be enough. Such wire will easily work with the measurement current.

Winding of course needs to be done with a machine, at about 0.2 mm pitch, you can’t do this by hand.

The elements were then measured to get the resistance corresponding to the workshop temperature, about 56 ohms, and fixed the wire in-place on the machine, with some super glue. Afterwards, the wire was further covered with high-quality epoxy, and fitted into a thin-walled aluminum cylinder, for added protection, and thermal equilibration.

The old sensor housing had still some stuff in it (the old Ni wire, and some stinky resin), and almost impossible to re-use the old mounting case for the sensor. Fortunately, we have a CNC lathe around, so quickly machined a new case as well.

A layer of Capton tape wound around the protected element, just in case of some leakage current developing over time.

The element was then put in the mounting case with some silicon-base thermal compound.

Finally, the sensor completed, connected to the old, steel wire braided cable.

For test, a litte fixture was made, which can be heated up with a 4 ohms, “100 watt” resistor. Well, it easily gets up to 150 degrees C.

As you can see, all working pretty well!

Some hours later, also the instrument fixed, dial and case sandblasted and painted, etc.


Field test!!

Length Endcoder Interface: reading the Heidenhain

This little post may help those that are dealing with rotating or linear encoders, and have been wondering how to build a circuit that actually works, and with a degree of reliability useful for industrial applications. Around machine tools, and similar equipment that rely on such encoders, there is a lot of electric (and audible!) noise, so most hobby circuits that just take some TTL signals and do some quick stuff and calculations won’t work. Let’s try with a real circuit and some good code.

Here is the device, it’s a Heidenhain ST1278, 10x interpolated TTL output micrometer.

According to the datasheet, it has a 20 micron grating, which will lead to a 2 micron signal period, allowing us to get 0.5 micron resolution.

After carefully opening the plug, which has the Heidenhain logo, and secret Heidenhain electronics inside, I can tell you, Heidenhain uses a 75ALS194 line driver, to drive the RS422 output.

We will be using a DS26C32ATM line receiver, to get the differential signal converted back to TTL level.

The differential lines is terminated in 120 Ohms (watch out for their dissipation, if you consider building this in SMD), and has two 220 pF capacitors to absorb and high frequency noise. This thing is running at 100 kHz max.

The output of the DS26C32 is going right to a ATmega328P, sitting on a Arduino nano clone, for convenience. This uses the common CH340G seriell to USB converter to talk to a host computer.

This is the full board. USB power is enough, even for the Heidenhain, and a HX711, which is also used in this device, for other purposes.

How to get the Heidenhain signals decoded into position. Well, we follow a sampling approach here, rather than using any of the rising edges, triggers, etc. – we just sample the two Heidenhain lines at 125 kHz, and compare the sampling result to the last result (of sample N-1), to determine if the Heidenhain moved forward, backwards, or not at all. If both lines change status -we know that something went wrong (e.g., if Heidenhain is moving to fast, or if some noise comes in despite all the effort to keep the noise controlled by the high current differential line).
The 125 kHz sampling is running on a timer-triggered interrupt routine. The duration of the interrupt can be monitored -at least in debug mode- by watching a test pin of the mega328P, by setting the test pin high when the interrupt is called, and clearing it once the service has been completed.

The initial software still used more then 4 microseconds for the sampling, a bit too much, this can be reduced to 2.4 microseconds, even without any special tricks.

Below, you can see the effect of a sampling error (introduced by very quickly pushing the sensor arm inwards), it takes slightly more time to handle the error.

Finally, all that remains is to communicate with the host – this is done at a data rate of 12 Hz, plenty for this application. The data interval is triggered by the HX711 load cell converter, and the the full dataset, including, current encoder reading, error count, load call reading, and time-stamp are transmitted to the host all in one packed, as hex encoded data, and at 19200 baud. All pretty fail-safe and slow, but working just fine, and still a lot of idle time on the line (see transmission pattern on the scope below)!

Below, the avr-gcc code performing all these wonderful tasks.

hhenc hx711 _180128.c

HP 85685A: another mains filter failure – Schaffner FN 376

With the 85685A repair complete, the instrument was subject the an extensive test, to make sure all is in good order and working stable. Well, it did work well for a while, then – PUFF! The mains filter blew, one of the infamous Schaffner filters that is designed to blow up after about 20 years of service. Schaffner is one of the only companies I stay away from for any design – it is a Swiss enterprise, but too many of their devices failed in my hands – their filters are often the first parts to fail, in high grade test equipment.

The 85685A, like most other HP gear, has the mains filter combined with a voltage selector switch.

Cutting it open, you can see the Wima MP3 cap, 47 nF, 250 VAC. The MP3 are metallized paper capacitors, rated for X2 (mains) service. All embedded in some black resin.

Copper wires of the choke showing trough.

New filters that match the FN 376 are hard to find, and new-old-stock, well, these filters might fail again. So I decided to go for a new filter, a Schaffner-free solution.

This will be the new filter – a ID-10AC-S, available for little money, and seem to be pretty good for their current rating.

The internals… the filter elements are nicely encapsuled in a two-shell plastic case. No potting compound!

The X2 capacitor, and the choke…

Transplanted to the Schaffner filter body… and wrapped with Cu tape, soldered closed, for EMI shielding. All well grounded!

From the datasheets, you these filter should have 20-30 dB loss at 1 MHz. Let’s put it to a test!

For the new assembly, tested with a 3585A, about 12 dB loss at 100 kHz, 30 dB loss at 1 MHz, should be good, and no modification necessary to the 85685A.

HP 85685A Preselector Repair: faulty attenuation

The HP/Agilent/Keysight 85685A Preselector is a great addition to any 8566B or 8568B spectrum analyzer. The preselector converts the analyzer into a test receiver, by increasing its dynamic range by 30 dB, down to very low noise levels.

Recently, I got a 85685A for repair, only knowing that it doesn’t work as it should. With some checks, it was very quickly evident that there must be a issue with the RF attenuator, or its driver.

This defect is clearly seen when looking at a test signal at various attenuation levels of the 85685A. The signal should stay at the same level, irrespective of the attenuator setting, but as soon as you go from 10 dB to 20 dB, the signal vanishes almost completely. This is not good.

This is the RF attenuator, a Wavetek OEM part. Unfortunately, there is no service manual for the 85685A available, so we need to figure it out by ourselves.

First, determined the switch matrix for the attenuator controls, by probing the control inputs at various attenuation settings. Pretty clear, there are 10 dB – 5 dB – 20 dB – 20 dB segments inside, which are activated by pulling the respective control input low. Easy enough.

After some disassembly of the case (removing the rear panel), you can get access to the four screws holding the attenuator to the case.
Notably, the case of the 85685A uses Torx screws, unlike most other HP equipment using this style of enclosure.

Underneath the label, there is now hidden screw to get to the internals of the attenuator, all is glued closed and sealed with silver epoxy. To break it open without destruction, I milled a small slot from the side of the unit. Probably could have milled a bit shallower, and a bit less, but OK.

With the slot, the lid is easily removed using a screw driver. Make sure not to bend the lid too much.

Looking inside, it is pretty obvious that someone must have fired a lot of power into the unit, when set a 20 dB input attenuation. Checked all other segments with a 8752A network analyzer, and all good, except for one of the 20 dB segments, as expected.

How does a 20 dB attenuator work? There are several topologies, Wavetek used a so call pi-arrangement of resistors. Only two of the resistors are blown, the output resistor is OK (this is also clear from the fact that most power is dissipated in the left two resistors).

The switching of the attenuator segments is done with miniature RF relais, similar to these. At over EUR 40 a piece – glad these are all good.

The relais are DPDT switches, soldered flush to the board (which is a PTFE composite board), for best RF performance.

For repair, we need to replace the resistors with good new parts – but there are hard to come by, with not even a Wavetek datasheet available for the attenuator, let alone, these parts.

Several attempts were made to get the best (lowest) SWR, and the best flatness, at very close to 20 dB attenuation.

First, used a combination of 1206 SMD resistors to get close to the values needed.

This is the flatness of the “good” 20 dB segment:

This is the flatness of the “1206 repaired” 20 dB segment:

Another style of repair, with the same parts, now soldered directly between the legs of the relais:

… no improvement, still quite some reduction of attenuation above 2 GHz.

Now, tried with a series arrangement of 0805 resistors for the 250 Ohm resistor (giving lower stray capacitance).

… quite some improvement!

Red is the good attenuator section, blue is the repaired section, at 0.2 dB/div scale!

I would call it good enough!

A quick SWR test (non-calibrated) for “through” and “actuated” setting of the repaired segment (and terminated in a 15 dB precision 18 GHz rated attenuator at the output) showed low SWR (keep in mind, the 85685A will only work up to 2 GHz anyway).

All sealed up with silver epoxy – a bit old stuff around here, but still working. And, used some Cu tape (with conductive glue, 3M type 3313), to make sure all is sealed well and forever.

Now, with the attenuator fixed and working, one more thing to consider – the power handling capacity. The 85685A is rated for up to 30 dBm (1 Watt) average power. Not sure if the SMD resistors used can handle it – they are a bit smaller than the original Wavetek parts. So I decided to swap the control lines for the two 20 dB segments. This way, the “good”=Wavetek segment No. 3 will always take most of the power, and the repaired section (SMD resistors) will only be needed for the highest attenuations, and never see any more than 10 dBm of power, even at the maximum allowable input. Still, I will keep a search going on a spare 0955-0235 programmable attenuator, for a reasonable price (some of these being offered for USD 100, which is a bit more than I want to spend for a 25 year old part of unknown nature and condition).

Finally, all assembled back together, and performed a flatness/attenuator test, by supplying a signal at -40 dBm from a 8642B generator. Measured amplitude at 1 kHz resolution BW is pretty flat over all attenuator settings and frequencies.

Let me know in case you have any 85685A units for repair….

Chair Repair: build in 1991, refurbished in 2017

My good old office chair has seen better days, with permanent use sind 1991, during all my study and overseas activities. At least, it is not a cheap imported chair, but a good old German made and top quality office chair, purchased for about 300 Deutschmarks in 1991. A very generous gift of my parents, who took care of my back even at those early days.
But now, all the fabric is work, and even holes showing up, and threads loose.

Sure, there are many professional repair shops that can do a full overhaul of such chairs, but what about the do-it-yourself spirit? So I decided to fix it myself, using simple tools, like, a nail gun (see below), a razorblade, some fabric (corduroy, available from a local shop at low cost), and a fleece (non-woven, anti-slip impregnated) fabric (about 100 g/m2 weight).

This is the nail gun I use, a Ferm ATM1042. It’s quite sturdy, and a great deal for the price!

The nails used are 5.8×13 mm, quite easy to worth with, using an air-pressure operated gun.

The fleece serves an important purpose, it covers the old fabric (nothing removed from the chair), and gives it some new firm touch. And, because of its anti-friction properties, it will not slip between the old and new fabric. And, it is available locally, at low cost. I used a single layer for the back rest, and two layers for the seat, cut to size.

Here you can see progress on the back-rest. Make sure the fabric is aligned property, then first fix two opposite sides with the needle gun. Then, continue with the perpendicular sides, then diagonally, and so on. Always apply an even “pull” to make sure the fabric looks nicely stretched around the corners. Avoid any wrinkles by pulling the fabric straight, and by applying more nails from the gun. After all, don’t safe on nails!

For the seating surface – the same procedure.

Voila, all done, and ready for at least 10 more years of service!

Manuals Additions: Motorola!

Thanks to a kind contributor, Mike, about 230 Motorola manuals have found there way into to archive. Included are various detail manuals and service guides of the GP series, and other quite popular Motorola radios.

Happy to receive any of your manual collections related to test equipment, high frequency electronics, or related fields. Will keep them online free of charge for everyone, and all well backed up.

| |– [8.7M]  6864115B18-D GP300 Basic Service Manual.pdf
| |– [421K]  AP-73 user manual.pdf
| |– [2.4M]  Astro Digital Spectra _ Digital Spectra Plus Basic service manual.pdf
| |– [3.3M]  ASTRO Saber Basic Service manual DigitalPort.pdf
| |– [1.6M]  Astro service software user guide.pdf
| |– [7.5M]  Astro XTL5000 basic service manual.pdf
| |– [1.9M]  Astro XTL5000 Detailed User Guide.pdf
| |– [7.9M]  ASTRO® XTSâ„¢ 2500 user guide.pdf
| |– [897K]  BPR_40.pdf
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| |– [1.8M]  CDM and PRO SERIES detailed service manual.pdf
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| |– [2.3M]  CEP400 basic user guide.pdf
| |– [6.2M]  CM140 basic user guide.pdf
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| |– [3.8M]  CM200 CM300 PM400 basic service manual.pdf
| |– [8.7M]  cm200 cm300 pm400 detailed service manual.pdf
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| |– [2.3M]  CM Radios Detailled service manuals.pdf
| |– [1.3M]  Commercial Series CM service information.pdf
| |– [160K]  CP140_160.pdf
| |– [8.4M]  cp150 cp200 detailed service manual.pdf
| |– [5.5M]  CP185 Service Manual.pdf
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| |– [7.0M]  Digital XTS 3000TM full featured model user_s guide.pdf
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| |– [8.1M]  disney2wayadv user manual.pdf
| |– [3.9M]  DM 3400 user guide.pdf
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| |– [8.4M]  DR 3000 basic service manual.pdf
| |– [8.4M]  DR3000 MOTOTRBO Repeater basic manual.pdf
| |– [6.9M]  DR3000 MOTOTRBO Repeater basic service manual.pdf
| |– [9.0M]  DR3000.pdf
| |– [ 79K]  Emergency Foot Switch instruction manual.pdf
| |– [5.2M]  EP450 basic service manual.pdf
| |– [1.5M]  EP450 detailled service manual.pdf
| |– [ 63K]  Flashing Adapter HLN9742 Service Manual.pdf
| |– [345K]  FLASHport user guide.pdf
| |– [4.0K]  GM1200E detailled service manual
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| | `– [924K]  GM1200E_SM _EN.pdf
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| |– [326K]  GM1200_UG_EN.pdf
| |– [889K]  GM1280 user manual.pdf
| |– [1.4M]  GM300 basic service manual.pdf
| |– [808K]  GM300 service manual (3 parts).pdf
| |– [ 14M]  GM300 service manual.pdf
| |– [217K]  GM340 user guide.pdf
| |– [4.0K]  GM350 installation manual
| | |– [440K]  350IN_EN.pdf
| | |– [ 25K]  350RS_EN.pdf
| | |– [ 74K]  350ug_en.pdf
| | `– [119K]  950rmkit.pdf
| |– [561K]  GM360 user guide.pdf
| |– [692K]  GM380 user guide.pdf
| |– [722K]  GM-660_Manual.pdf
| |– [871K]  GM series Radio Installation manual _ service manual.pdf
| |– [119K]  GM Series service information.pdf
| |– [3.3M]  GP1280 basic service manual.pdf
| |– [1.9M]  GP1280 user guide.pdf
| |– [4.0M]  GP300 Basic service manual.pdf
| |– [231K]  GP300 Service manual (schematics).pdf
| |– [1.9M]  GP320 user guide.pdf
| |– [8.4M]  GP328 GP338 Detailed service manual.pdf
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| |– [453K]  GP328plus GP338plus GP338XLS Basic service manual.pdf
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| |– [4.1M]  GP330 user guide.pdf
| |– [1.9M]  GP340 Ex Portable Radio basic user guide.pdf
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| |– [3.4M]  GP350 service manual.pdf
| |– [4.0K]  GP350 User Guide
| | |– [374K]  gp350_part1.pdf
| | |– [1.5M]  gp350_part2.pdf
| | `– [703K]  gp350_part3.pdf
| |– [1.8M]  GP360 user guide.pdf
| |– [2.8M]  GP380 Ex Portable Radio basic user guide.pdf
| |– [1.9M]  GP-380_Manual.pdf
| |– [1.2M]  GP388 user guide.pdf
| |– [4.4M]  GP580 Ex Portable Radio basic user guide.pdf
| |– [4.0M]  GP600 series Basic Service manual.pdf
| |– [2.2M]  GP640 GP680 Basic Service manual.pdf
| |– [1.8M]  GP640 GP680 Basic User Service manual.pdf
| |– [2.2M]  GP-680_Manual.pdf
| |– [1.3M]  GP68 User Guide.pdf
| |– [4.0K]  GP Series detailed service manual
| | |– [384K]  B32E_Sect1_Service Maint.pdf
| | |– [518K]  B32E_Sect2_Keypad_A3.pdf
| | |– [ 89K]  B32E_Sect2_Keypad_A4.pdf
| | |– [576K]  B32E_Sect3_Controller_A3.pdf
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| | |– [2.6M]  B32E_Sect4_VHF_A3.pdf
| | |– [255K]  Chap 1 Introduction_A4_v0.pdf
| | |– [234K]  Chap 2 Theory of Operation_A4_v0.pdf
| | |– [718K]  Chap 3 Maintenance_A4_v0.pdf
| | |– [551K]  Chap 4a Controller and Keyboard Info_A3_v0.pdf
| | |– [240K]  Chap 4a Controller and Keyboard Info_A4_v0.pdf
| | |– [525K]  Chap 4b VHF Info_A3_v0.pdf
| | |– [510K]  Chap 4c UHF1 Info_A3_v0.pdf
| | `– [511K]  Chap 4d UHF2 Info_A3_v0.pdf
| |– [9.3M]  GR300 GR500 service manual.pdf
| |– [2.3M]  GTX LCS 2000 service manual.pdf
| |– [968K]  HF-SSB Automatic Antenna Tuner owner_s manual.pdf
| |– [573K]  HKLN4197A_PRO2150_Eng.pdf
| |– [9.3M]  HT1000 JT1000 MT2000 MTS2000 MTX series Service manual.pdf
| |– [477K]  HT1000 MT2000 MTS2000 MTX series Service manual.pdf
| |– [4.3M]  HT1250 user guide.pdf
| |– [4.9M]  HT750 HT1250 MTX850 MTX1250 MTX8250 MTX9250 basic service manual.pdf
| |– [1.9M]  HT750 HT1250 MTX850 MTX1250 MTX8250 MTX9250 supplement basic service manual.pdf
| |– [ 12M]  HT800 VHF service manual.pdf
| |– [3.0M]  HT90 service manual.pdf
| |– [2.2M]  HT Series detailed service Manual.pdf
| |– [2.2M]  LCS2000 service manual.pdf
| |– [1.4M]  LTS 2000 user_s guide.pdf
| |– [6.9M]  Mag One basic service manual.pdf
| |– [1.7M]  MagOne Basic Service manual.pdf
| |– [433K]  Mag One BPR40 Brochure.pdf
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| |– [2.1M]  MCS2000 service manual vol-1.pdf
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Rigol DS1052D=DS1102D Oscilloscope: encode issue fix

For about 8 years, I have been using a Rigol DS1052D 50 MHz scope (which works up to 100 MHz with a well known software fix), but recently, it has given me some grieve: the knobs turn, but the settings jump, both for scale and time base. This is quite annoying – trying to fix something, with broken tools or scopes, is no fun.

Already expecting the worst, like, mechanical failures of the scope of encoders, or some strange software bug (because all encoders were affected at virtually the same time), I decided to open up the scope. Easier said then done. There are 4 screws, two of which are under the handle, and you have to remove the powder on button with some bent wire (don’t scratch the case!). Then, move around the back cover, eventually, it will come off! Don’t give up! Don’t remove the screws of the power input socket!

Once inside, you need to take off the two screws for the D9 connector, and then, several more screws to take out the power supply, before you finally get to even further screws holding on the front panel.

Before taking any soldering iron to replace the encoders, as suggested by some folks on google, I tried to use the magic DeoxIt D5 to clean up things and to get it going again. Just spray some of the stuff into the encoders, there are some small openings (circled red on in the image). Turn the encoders to make it work. After a while, clean of any excess D5, don’t let it get in touch with the rubber of the DS1052D buttons – most rubber can handle D5, but better not try your luck!

And, it worked like magic. Not only are the encoders working again, but also the feel of the knobs is much better, not as sticky as it used to be.

Xmas Cookies: Heidesand

It’s never to early to prepare for Xmas, and certainly not too early to bake some cookies anyway.

These cookies are a specialty of our family, called “Heidesand”, but it is a modified recipe, and a bit different compared to the Northern German original.

For the dough, thoroughly mix and knead:

250 g butter (soft)
100 g finely powdered sugar
100 g marzipan paste
300 g wheat flour type 405

The dough will be rather soft after some kneading, but don’t worry!

Form to rods of about 1″ diameter, wrap in aluminum foil and let cool/solidify in the fridge overnight.

Cover with some egg jog, and roll in sugar to fully cover the outside with crystals.

Immediately cut in slices, about 3/8 of an inch thick. Put on non-stick paper with a good distance between the slices. Don’t let the rolls warm up! For best results, only cover one roll with the sugar coating at a time, and cut it into slices, before proceeding with the next roll.

Bake at 175°C, circulating air oven, for about 11 minutes (perimeter of the cookies must be brown, inside only lightly colored).

Everything done right – the cookies will look like this, and taste even better:

SimonsDialogs – A wild collection of random thoughts, observations and learnings. Presented by Simon.