Discussion in 'Exclusively Sansui' started by steveUK, Mar 15, 2017.
Yupe, you could check the molex connectors on F2541 too
Molex connectors? Not a known that's known to me..
Picture Credits: some random guy from the internet
Probing and pushing around on the power supply board results in either a sound output, or no output as the case may be. The problem is, this is not a classic intermittent fault such as is often caused by a dry joint whereby it is possible to 'zoom in' on a specific physical area or position on a PCB that triggers change. No, instead, the sound gradually fades in and out, making it difficult to locate a 'hot spot'. So I'm thinking that it's a faulty component that is fading in and out rather than a poor connection. More testing to be done tomorrow, it's evening here now in the UK, workshop locked up, raining outside, somethings never change.. ;-)
I've disconnected and cleaned those ones. Actually they looked pretty good, gold plated even.
so the sound fades in and out when you poke the power supply pcb; does that suggest that capacative storage is feeding the amp after your poking has disrupted the DC rail supply?
It suggests to me a faulty component - passive or active - that is intermittent. I'm going to go through them one by one today hopefully. Still early morning here. Just got up to make cuppa tea for me and GF. Not raining though.. Oh, might have to do some work in the garden too..
Today I've been checking voltages around the power supplies board and I'm pretty sure that TR03 is intermittently faulty. Poking it with a paxolin rod not only invokes the sound to come and go - it fades in and out - but the voltages around it also change in sync with that effect; ie correct voltages when the sound is there, and wrong when the sound disappears - as you'd expect really. I'm waiting for the new parts to arrive, I've bought replacements for all three of the transistors in that area. And I've changed the electrolytics on that board. Oh yes, TR03 trannie is also very slightly microphonic; a sure sign of a faulty transistor in my experience.
Regarding the lamps not lighting, I've come to the conclusion that the selector switch is faulty in ways that cannot be fixed by merely using contact cleaner spray (my lamps would be the brightest ones on the planet if that was the case...). Looking at the wafers from the side (all the boards in place, nothing dismantled) the contact tracks that come out to the PCB are hollow pin riveted in place on the wafer. My guess is that some of these rivets are home to poor electrical connections, and as rotating the switch does not actually clean them (the riveted connections), then it would need a strip down and those rivets augmented by soldering. But then again, maybe these rivets just provide a mechanical function, not electrical? I'm not sure. Anyway, once the sound fault is sorted I guess I will have to bite the bullet and dismantle the set enough to get at the switch and figure out what's going on. Any tips re removing that switch? there seems to be hard wired connections at both ends of that input selector board - not easy when you want to get at the other side..
lift the complete tuner tray off to get topside access
Ok thanks, exactly what level of, and procedure of dismantlement is that?
For now, just so that I can see just which lamps are not faulty I have performed the illumination mod. From what I can see, all the scale bulbs seem to be working (yes?) as do the signal meters. As already identified and mentioned, one in each of the power meters lamps are not working. But what about the individual input selection ID lamps - FM, AM, AUX etc? - will they only work when I get the selection switch working?
Ya, all the lamps are controlled from selector except the power meters
Getting the switch removed is not that hard, take pictures of what wire goes where and it will come out after you disassemble the pot shaft and unsolder the legs. Don't let your iron sit too long as the old pads can lift !
I have done it several times without removing the tuner assembly...
Ok thanks, but having done the illumination mod, I'm not sure if the input selection ID lamps should have all illuminated too?
no, the selector lamps still should function as normal..
I've now fitted a replacement TR03 on the power supplies board and the sound now comes on instantly, no fading in and out, so clearly that was the fault. I have also replaced the selector switch with a new one. I could actually see what was wrong with the old one while it was in situ, one of the main pole connectors was not pressing down on to the central rotating track. I tried all ways for a long time to get it to press down on to the track, but I just can't get at it well enough to bend it in the right way, so change it was. I reversed the illumination mod, so now the selector switch performs all the functions that it should. The 'FM' lamp does not light up (all others do) so I need a bulb for that and also two for the power meters. So, my next task is to source those bulbs then perform the difficult task of replacing the ones in the power meters..
Alright! Nice job...
Thinking about it, surely it's possible to solder some leads on to white LEDs for the function and power meters? Anyone done that and can advise type numbers, series resistor values etc etc? Or a link? Thanks.
Contact member Dwojo.... He's got lamps/ LEDs for anything!
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