• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

I need help with a power supply problem.

Found it.

4765ef54-ad4d-45d4-8a69-eb833ffebbd3.jpg

That is one complicated puppy! Click on the image to enlarge.
 
the voltages are listed so this might be easy to narrow down.

What are the voltages at R19/R20?

This is the output (pin 4) of the power packs. the resistors might be easier to measure if your eyes are suspect.
 
Mr Boochie said:
Found it.

4765ef54-ad4d-45d4-8a69-eb833ffebbd3.jpg

That is one complicated puppy! Click on the image to enlarge.
Click to expand...
That’s it. I have to use my cellphone camera as a microscope to look at it. But it has everything needed. What happened is everything was working but the 10000 mfd power supply caps were both down to just around 5900 mfd. when I put new caps in the weak transistors at Q7, Q10, and Q11 took a dump. They all were already heat stressed and had the black leg syndrome. It also took out D7. I have new components on the way. This circuit feeds the tuner and the safety circuit. That’s why the relay wasn’t picking up
 
rickl said:
the voltages are listed so this might be easy to narrow down.

What are the voltages at R19/R20?

This is the output (pin 4) of the power packs. the resistors might be easier to measure if your eyes are suspect.
Click to expand...
I checked the power packs and they seem to be within spec. I did find the voltage differential transistors in the safety circuit were open.
 
rickl said:
the voltages are listed so this might be easy to narrow down.

What are the voltages at R19/R20?

This is the output (pin 4) of the power packs. the resistors might be easier to measure if your eyes are suspect.
Click to expand...
I will measure R19 and R20 tomorrow. Been painting the living room all day. Just a little worn out. I appreciate everyone helping. I took a 15-20 year break from working on electronics and I’m very rusty. Not to mention old!
 
rickl said:
Let's see what the new parts do. @mbz said you answered this in post #11
Click to expand...
I’m sorry. I did answer that. 150-160 MV. I didn’t realize R19 and R20 were connected to pin 4. I measured straight at pin 4. I was looking at the back side of the board. This unit doesn’t come apart easily for service.
 
...AI suggests the receiver was built by Setton and is identical to the Setton RS 440. You might want to download documents (owners, service, schem, test and what not the sites carry) about it as well to cross-check it; perhaps there's additional useful info to be found.

1789460911485.png
 
borchee said:
...AI suggests the receiver was built by Setton and is identical to the Setton RS 440. You might want to download documents (owners, service, schem, test and what not the sites carry) about it as well to cross-check it; perhaps there's additional useful info to be found.

View attachment 3837023
Click to expand...
I have already looked at the Setton schematic too. They are the same circuit.
 
Mr Boochie said:
8e0e225b-5942-4ab2-a52e-f8ca9fe7e23e.jpg

Here's a close-up of the power supply and output stage, if that helps.

:)
Click to expand...
I just wanted to clarify that the transistors I found bad are on the tuner board. I’m hoping I don’t have anything wrong on the amp board. I’ll need to check. It’s showing good on pins 1 and 4 of the power packs. The amp board is hard to troubleshoot without desoldering the output modules and removing the board from the heatsink. I’ve already done it twice and don’t want to ruin the traces.
 
I'd verify the voltages at the protection circuit. if pins #4 of each power pack is low and the relay isn't triggering, this should be the first thing to fix (imho).

pins #3, 7 should be +- 0.03v per schematic.
 
Jon Fox said:
I just wanted to clarify that the transistors I found bad are on the tuner board. I’m hoping I don’t have anything wrong on the amp board. I’ll need to check. It’s showing good on pins 1 and 4 of the power packs. The amp board is hard to troubleshoot without desoldering the output modules and removing the board from the heatsink. I’ve already done it twice and don’t want to ruin the traces.
Click to expand...
13768f0d-8cee-4500-9d19-4c70e76728b6.jpg



________________________________________
4d225992-f4b1-4987-90aa-004218536924.jpg
 
Mr Boochie said:
13768f0d-8cee-4500-9d19-4c70e76728b6.jpg



________________________________________
4d225992-f4b1-4987-90aa-004218536924.jpg
Click to expand...
I truly appreciate your support. I just finished taking the amp board apart again and found Q1 and Q2 are both completely open. These will definitely keep the safety relay from latching. I have modern replacements on the way. These are the 2SA798 5 leg transistors. I’m assuming since every component I found open and had black leg disease that the new power supply caps were too much for them. The original caps were very unhealthy and only displayed half their original value.
 
I think I used 2 matched ksa992 for each a798. Buy 10 and you should be able to find ones close enough. These are on the naughty list.
 
Jon Fox said:
I truly appreciate your support. I just finished taking the amp board apart again and found Q1 and Q2 are both completely open. These will definitely keep the safety relay from latching. I have modern replacements on the way. These are the 2SA798 5 leg transistors. I’m assuming since every component I found open and had black leg disease that the new power supply caps were too much for them. The original caps were very unhealthy and only displayed half their original value.
Click to expand...
You are welcome! Are those Hitachi ICs okay? Are they even available anymore?
 
You must log in or register to reply here.
Back
Top Bottom