Ok, I've ordered the 2 caps that looked bad and the 4 mentioned by amplitude and 3 more on the power board.
Thanks one and all I will keep you posted on my progress.
There appear to be 50-60 capacitors listed (I didn't count them) would all of them have to be replaced on a re-cap, or are some good "forever"?
MAACO, Thanks for getting back to me, but it sounds like a different problem, literally.
Thanks one and all I will keep you posted on my progress.
There appear to be 50-60 capacitors listed (I didn't count them) would all of them have to be replaced on a re-cap, or are some good "forever"?
MAACO, Thanks for getting back to me, but it sounds like a different problem, literally.
You could, with benefits, have ordered capacitors with more Uf in the rectifier area, all 4700uf capacitors, modern capacitors in same size have more storage, as long as the fit..
Thanks amplidude, this will be the first time getting in this deep into a component, so I'm going to try to keep it as straightforward as possible.
Maybe next time I'll consider amping it up, so to speak.
Maybe next time I'll consider amping it up, so to speak.
So I replaced the 4 main caps on the power board with no success in stopping the motorboating.
I replaced the next largest caps on the main board and that did the trick. No more motorboating.
I was somewhat surprised that it wasn't the main caps that were the culprits, not sure why, I just figured they would be the ones.
Thank you one and all for pointing me in the correct direction to get this sorted out.
Thats the good news, bad news is I was trying to figure out the current to the lamps so I could source new ones and when I touched the multimeter to the bulb leads the unit went dead. I had already checked voltage at 5.96V.
I've checked all the fuses they are all fine, not sure what to check next, the protection circuit? Main power switch?
I replaced the next largest caps on the main board and that did the trick. No more motorboating.
I was somewhat surprised that it wasn't the main caps that were the culprits, not sure why, I just figured they would be the ones.
Thank you one and all for pointing me in the correct direction to get this sorted out.
Thats the good news, bad news is I was trying to figure out the current to the lamps so I could source new ones and when I touched the multimeter to the bulb leads the unit went dead. I had already checked voltage at 5.96V.
I've checked all the fuses they are all fine, not sure what to check next, the protection circuit? Main power switch?
The one's on the amp are closer to where the positive feedback was operating that gives motor-boating. There may be some RC filtering involved, especially to the input stage, and that R "distances" the main filter caps from the place where capacitance matters for stability.
If there's a protection circuit which has electrolytics I would think about possibly replacing these - if they go out of spec the protection circuit can play up, which could lead to issues, and even lead to it failing to protect (or spuriously going into cutoff) - this seems to crop up regularly as an issue in older amps here and is probably worth anticipating.
Its only electrolytics that go dry with age, and if there are many you can wait for issues to arise (replacing them all carries some risk of track-lifting or error and can be quite tricky and arduous). But I'd suggest making an exception for protection circuitry.
Thanks for the reply Mark, here's a picture of the "device" that doesn't seem to be doing its job anymore. It used to be engaged when first turning on the unit (a corresponding red light would light up) and after 2-3 seconds there would be an audible click from this unit and the unit would be operating, red light out.
Now there is no red light and nothing from this device, circuit?
Now there is no red light and nothing from this device, circuit?
Attachments
That's a relay, presumably the speaker protect relay. Perhaps the circuit driving it is damaged? Perhaps the supply for this and the lights is blown? A regulator perhaps?
This is the sort of probe to use inside busy electronics enclosures to prevent shorting things out: https://uk.farnell.com/hirschmann-t...-SHOPPING-TEST-MEASUREMENT-NEWSTRUCTURE-20APR
This is the sort of probe to use inside busy electronics enclosures to prevent shorting things out: https://uk.farnell.com/hirschmann-t...-SHOPPING-TEST-MEASUREMENT-NEWSTRUCTURE-20APR
Ok Thanks, I'll go over the unit and follow the light circuit and see if anything looks obvious. There is still power to the unit, and the stereo light comes on, but nothing is going to the power meters or speakers.
Hi, John! Have you fixed problem with protection module of your SR-804? If not, I'm think you need check protection circuit of IC501(HA12002). I mean, you need check fuse F002,then measuring Vcc on resistor R504, then check cap C502. By the way, you have got the Service Manual SR-804 ?
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