ReynaldoGonz
New Member
What do you think about source flutuations? Any clue?
i think it is something more, I cleaned up again those switches and checked continuty and everything is ok.The TAPE MON and FUNCTION switches need a thorough cleaning.
The supply voltage to the unit may be a bit high. That would explain the higher bus voltages.
Is this a multi-voltage unit with an input voltage selector?
125 VACWhat is the measured AC supply voltage?
Yeah, I saw at 1st time and tought same thing (why black painted?, maybe some burned component beside of them on other times). Gonna check every component on energy supply section unsoldering and soldering one by one, and I don't know if could be a good idea to change them whole kit, I think are one of the most work demanded compontents of whole unit.might be the pics but diode looks blackened above the 3 heat sinks
It could be Q25 that is a regulate voltage transistor. It supose to be a 13.5 VCD source but I have 10.4 VCD.regular diodes can be checked in circuit .main failure rate is short . or open . 600mv or so on diode test it is good .
no need to lift one side if testing good in circuit in most cases .
I already resolded Q25 some time ago and I'm thinkin to clean and add thermal grease and add another heat sink plate to Q25 but first fix this problem. Thank youSuggest to read the schematics and measure all the voltages that they print on them (esp the power supplies), identify what does not match within 5-10% tolerances. Tabulate what is out of spec.
Q25 regulator supplies ~13V to many places.
A lot of times the transistor gets so hot that it creates a bad solder joint, touch up the solder joints on Q25
Q25 is controlled by D4, which is a 14V zener diode.
Test the voltages at R1 to verify adequate voltage at the collector of Q25. R1 is the ceramic/cement resistor clipped to the main heat sink.
Measure the voltages at all three legs of Q25, as well as Q19 an Q17, then post them here.
It is 38.6 VCD, in attached draws are voltages.The voltages you report at R1 should be acceptable. One side should be 52V, and the other side 26V. Since your reported line voltage is about 7% above the design voltage, your measured voltages should be reasonable.
The most important thing is that there is about 26V at the collector of Q25. It should be able to regulate the 13.2V supply as designed.
As mentioned before, we need to know the voltage at the emitter of Q25.