Ugh, another post, sorry. I decided to recheck components I thought I'd checked before; one of the transistors I'd replaced seemed to have a short but I tracked that down to another bad transistor, I think a driver, the label is C1735 27D (which I assume is a 2SC1735), manufacturer unknown. (It is TR316 on 22asd's nice photo, near the transistor that had been a 2SC2577, is now a 2SC4466.) I can't find anything else, but I also can't verify whether or not it was already fried before I soldered in the new transistors; I thought I'd checked this line for shorts, but my life is a succession of senior moments.
So, two questions: (1) is there any way to identify the manufacturer of one of these transistors, and does it matter, and (b) now that I've pulled the bad transistor, would it be completely idiotic for me to try powering up the amp again (through the dimmer) just to see if there are signs of other problems?
So, two questions: (1) is there any way to identify the manufacturer of one of these transistors, and does it matter, and (b) now that I've pulled the bad transistor, would it be completely idiotic for me to try powering up the amp again (through the dimmer) just to see if there are signs of other problems?
The manufacturer doesn't really matter and to identify it you would have to match any image/fonts to those known to be associated with the manufacturer.
Bad luck on the bulb
You can always power up with a bulb to see what happens but tbh if you were to stand any chance of fixing this then you need to be prepared to put some effort into a methodical diagnosis and test procedure.
Bad luck on the bulb
You can always power up with a bulb to see what happens but tbh if you were to stand any chance of fixing this then you need to be prepared to put some effort into a methodical diagnosis and test procedure.
So I started looking for something in the PS; there's a short in the primary on the transformer. I didn't find this before since I was tracing without a working fuse in the receiver (doh!). What a waste of time! Time to put the thing into storage, until I stumble across a working replacement.
Yeah, you're probably right. While I wasn't expecting 0, I only got 5ohms on the resistance, which I assumed was low for such a long stretch of wire. I don't really know how to test it otherwise without removing it from the circuit. I can test it as an inductor, but the value (11H) doesn't really say much to me.
It would be extremely unusual for a primary to be short or have shorted turns. It is going to be fine.
The 'reactance' of an 11H coil on its own would be:
XL= 2Pi*F*L which is 4146 ohms if F is 60Hz.
That gives a primary current of 115/4146 which is approx 27 milliamps rms.
Your transformer has other things influencing it such as the effects of the secondaries and any mutual coupling that occurs but you get the idea...
The low DC resistance gives no clue to the AC current that will flow.
One test if you are really unsure is to just disconnect the secondaries and power the primary up on its own. The current flow should be as described above... minimal... and the secondary voltages should all be correct.
The 'reactance' of an 11H coil on its own would be:
XL= 2Pi*F*L which is 4146 ohms if F is 60Hz.
That gives a primary current of 115/4146 which is approx 27 milliamps rms.
Your transformer has other things influencing it such as the effects of the secondaries and any mutual coupling that occurs but you get the idea...
The low DC resistance gives no clue to the AC current that will flow.
One test if you are really unsure is to just disconnect the secondaries and power the primary up on its own. The current flow should be as described above... minimal... and the secondary voltages should all be correct.
At this point, if it is the transformer then it isn't worth pursuing until/unless I can source a replacement, and if it is not the transformer then I have more diagnostic tasks ahead of me than I have time for right now (since my obvious repairs didn't work, and I haven't found any other faulty components). Either way, the project has to go on hold, either for a while or forever. While the receiver had a very nice sound when it worked (warm and rich coupled either with our Klipsch or with our Polks), it was not especially high-end, and I think I've gone long past diminishing returns on my time.
(It would have been helpful to at least have a service manual, without one I don't even know what the secondary voltages on the transformer are supposed to be. I was able to get manuals for a couple of nearby models, but they didn't give me much useful information.)
(It would have been helpful to at least have a service manual, without one I don't even know what the secondary voltages on the transformer are supposed to be. I was able to get manuals for a couple of nearby models, but they didn't give me much useful information.)
99.9% it is not the transformer it will just be a normal failure mode of an amplifier.
It is difficult without a manual but the transformer test is easy and secondary voltages can be estimated from the circuitry it powers... but in practice you don't need worry over any of that... if it powers up normally on its own it is 99.999999% going to be OK.
it will just be a normal failure mode of an amplifier.It is difficult without a manual but the transformer test is easy and secondary voltages can be estimated from the circuitry it powers... but in practice you don't need worry over any of that... if it powers up normally on its own it is 99.999999% going to be OK.
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