CJ PV6 question

[kwingylee]

Guys:
I have been using my modified PV6 preamp for many years. Last weekend, I ceased getting output from it. It has been driving MV50 / MV55 amplifiers.
I was able to measure voltages out of the power supply and getting 0V across C6. Looking at the schematics, it looks like Q2 and Q3 are the culprits. The parts list showed these to be MPS-A42 and MJE 340 transistors. I am in the process of ordering their replacements.

However, while I have it opened, I also want to replace Q4 and Q5 for preventive maintenance.
The parts list show these to be 2N3904 and MJE182. These are not the parts on my board. Instead, I have Motorola 2N5061 and 2N4870s. As far as I know these are not direct replacements to the parts listed devices.

Can someone help me confirm the part numbers? To play it safe I want to put in the Motorola equivalents and not what is listed in the parts list.

Thanks in advance.

Kwing

[admin]

Hi and welcome to CJO.

If it was working well before, I don't see why you couldn't replace the parts with what was in there (regardless of what the schematics say).

[kwingylee]

I was able to replaced Q2 (Motorola MPS A42) Q3 (MJE 340) D17 and D18 (1N4007). The high voltage supply works now (400Vdc). I did not replace Q4 and Q5 even though I bought replacements for them. The Omron MX2P-0-US-12VDC (now unobtainium) tripped as expected, I am reading 55Vdc across D2 (1N4148 cathode) before the relay trips and 48Vdc after it trips. The Anode reading is 55Vdc before and 37Vdc after the relay trips. The voltage differential is 11Vdc so that seems to work. So far so good.

[roberto]

Hola,
Conrad Johnson advice is to replace all the regulator transistors...even that only one is the culprit. It is a safe move, due to we don't know if one of those might suffer.

Usually while doing a replacement transistors, I use more power dissipation and more Ico current value. Working voltages too, of course.

Great to know that you did find the culprit!

Happy listening!