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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon May 06, 2013 9:35 pm Post subject: |
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Ok, good. After you get that resistor replaced and verify we are back to where we were then recheck those 2 pins, 8 and 11. Don't worry about the 15v line. Pin 8 should be a neg voltage and pin 11 should be a positive voltage and they should be around the same value. Let me know what you get.
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Mon May 06, 2013 10:27 pm Post subject: |
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Replaced the resistor but no luck unfortunately, same behaviour; click, click, click, click, click, click 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon May 06, 2013 10:36 pm Post subject: |
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Does the display come on at all? What relay is clicking?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon May 06, 2013 11:15 pm Post subject: |
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Probably should recheck both those regulators, ic101 and ic102. If it took out that resistor it's a good possibility it took out 1 or both of those regulators.
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Mon May 06, 2013 11:37 pm Post subject: |
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It sounds like RLY103 but I can't be certain; both regulators check out okay; there's very little voltage even GETTING to them though. Like 2-3 volts across one and less than a volt across the other (PD across the ground & in pins).
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon May 06, 2013 11:48 pm Post subject: |
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Ok, 1 more wild test and if you don't find it we are going to start from scratch. You need to DMM on diode test and check D127, D124, D123, D122, D121 and D125. You will show leakage both ways but 1 or more may show real close to zero if bad. If unsure, you will have to lift 1 leg on each to properly test. The feedback short that took out the resistor may have taken out 1 or more of these suppressor diodes. Fun, fun.
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Tue May 07, 2013 12:09 am Post subject: |
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Wait, one more piece of information for you, and this one's REALLY weird.
Firstly, it's RLY106 (the thinner one near the AC input) which is triggering repeatedly, which in turn was triggering ALL of the relays (giving the unit an almighty shake every time), eventually they would stop triggering, and RLY106 would carry on by its lonesome.
Okay, so this is where it gets really weird. I swapped out 7815 with the one I originally pulled from the unit (and was WORKING originally), and after a couple of false starts, the unit now powers up (with the preamp board removed). Now this is where it gets weird... the 7815 is registering 2V output, and the 7915 is registering -0.5V output.
I'm assuming that they're both buggered, but... why isn't the protect triggering anymore? And why is the unit even still on? Oh, and here's the REALLY weird bit; still measuring 52V from speaker ground to Darlington emitters. So where the hell is that 50V coming from if not the voltage regulators?
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Tue May 07, 2013 12:14 am Post subject: |
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I feel like doing an Arthur Dent, standing on a boulder and proclaiming "I will go mad" 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue May 07, 2013 12:16 am Post subject: |
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Forget about the 52v for now. Lets get these regulators straightened out. First off, don't use speaker ground as ground to test those regulators. Use the ground pin of the regulator itself to test. And then test both input and output and give those numbers of ic101 and ic102.
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Tue May 07, 2013 12:21 am Post subject: |
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| macgyver655 wrote: | | Forget about the 52v for now. Lets get these regulators straightened out. First off, don't use speaker ground as ground to test those regulators. Use the ground pin of the regulator itself to test. And then test both input and output and give those numbers of ic101 and ic102. |
I was testing from the ground pin  Lemme just check the ins. I've got a spare set of regs so if I have to replace them again its not the end of the world; only one I don't have a spare for is the 7805R.
Checked the diodes as well and they're all a-ok.
7815 is 3.8V in, 7915 is 2V in. Outs are the same as before.
Oh, and I know what actually makes the unit stay on now; measuring the voltage across the 7915's ground and out pin, for some reason, lets the unit switch on and STAY on.
EDIT: Gotta hit the sack now, been up for 48 hours and if I stay up any longer I'm going to get even more sloppy than I already am. Will check back first thing tomorrow I'm guessing the advice will be to replace the regs lol
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue May 07, 2013 12:35 am Post subject: |
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Those inputs are way to low. Set your DMM to AC and at CP104, test between pins 5 and 4 and then between pins 5 and 6. Give me those voltages.
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Tue May 07, 2013 5:33 pm Post subject: |
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19 Volts through both.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue May 07, 2013 7:01 pm Post subject: |
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Ok, leave it set at AC and keep 1 test lead in cp104, pin 5 and then test both legs of C141 with the other lead. Give me the voltages of each leg.
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Tue May 07, 2013 7:34 pm Post subject: |
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Right; viewed from above, with CP104 at the bottom and C141 above it, the left hand leg of C141 is at 0.6V and the right hand leg is 3.8V.
EDIT: Looks like the R141 I replaced has gone duff again; getting 0V out of it. when measured between pin 5 and the output leg of the resistor. Also, got 19V going into R142 and 3.8V coming out.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue May 07, 2013 7:56 pm Post subject: |
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| mdc wrote: | Right; viewed from above, with CP104 at the bottom and C141 above it, the left hand leg of C141 is at 0.6V and the right hand leg is 3.8V.
EDIT: Looks like the R141 I replaced has gone duff again; getting 0V out of it. when measured between pin 5 and the output leg of the resistor. Also, got 19V going into R142 and 3.8V coming out. |
You guessed it. That was my assumption. Both resistors blown.
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Tue May 07, 2013 8:32 pm Post subject: |
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Well I'm officially out of parts now; will need to make a list for RSonline.
Any suggestions? I'm guessing it'd be worth grabbing a few 0.047uF caps for between the transformer and the regs, along with those .22ohms?
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Tue May 07, 2013 9:04 pm Post subject: |
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Success! I managed to find a couple of 0.22 1Ws in my parts drawer, and the unit powers up (without the preamp board attached; that's still missing a couple of components).
EDIT: Both voltage regulators read well within tolerance (14.93V and -14.85V), so looks like replacing those two resistors did the trick
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue May 07, 2013 9:26 pm Post subject: |
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Good. So now we are back to the 56v on the output line. Go back to CP505 again and check DC on pins 8 and 11 using a speaker ground for negative. One pin should be a pos voltage and one should be a negative voltage.
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Tue May 07, 2013 10:04 pm Post subject: |
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Affirmative. +54V and -54V.
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mdc
Joined: 30 Apr 2013
Posts: 50
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| Posted: Tue May 07, 2013 10:12 pm Post subject: |
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Aaaaand both those resistors just went poof again.
Now I definitely need to order some more components lol.
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