Tag Archives: Dual

Dual CV 1600 Stereo Amplifier: a real HiFi classic with some capacitor smoke, and a very large dropout voltage regulator

This one is a real gem, a stereo amplifier, Made in Germany, and nicely constructed in the 1970s, using mostly discrete parts.

cv1600 front

Some issues are common to all old amplifier, like, defective switches, aged contacts, and so on, but these can be fixed with good contact spray, or by (mechanical) repairs. For the CV 1600, most common fault is the X2 mains capacitor, 47 nF, which will eventually turn into smoke and stench. Be sure to replace this part, if you have a CV 1600.

The 47 nF X2 rated cap is located on a fuse board, and to get access, you need to remove all the transistor wires. This is best done with great care, and without damaging the wires, otherwise, it is quite laborious to connect everything back up again.

sdr
sdr

This CV 1600 also had another issue, no signal from the distribution amplifier board. Some first check showed issues with the +15 V rail being stuck at ~7V. Probably a defective Tantalum or other capacitor? Probably not – not much current flowing either, so it is not related to a short at the output.

dav
dav

Inspecting the regulator – it is a TO-202 LM341p15, pretty rare nowadays.

dav dav[/caption]

No heatsink on the regulator, so I got a bit worried with the dissipation of TO-202 vs. TO-220 devices – all I have in stock are TO-220 regulators, LM78xx series.

cv1600 to202 vs to220

lm341p15 to202

lm7815 to220 heat resistance

After inspection of the datasheets – nothing to worry about. Pretty similar heat resistance, junction to ambient. Voltage drop is about 10 V, current roughly 50 mA, so, 0.5 W – roughly 30 K temperature rise.

A quick test with a 5.6 Ohms, 250 W dummy load showed no further issues (except an incorrectly installed signal cable, probably from an earlier attempt of someone else to fix this unit?).

Finally, some performance data of the CV 1600.

cv1600 data