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Bose 1800 series VI Pro amplifier not turning on & Peavey PVi 3000 no output
Bose 1800 series VI Pro amplifier not turning on & Peavey PVi 3000 no output
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Old 13th November 2019, 08:01 PM   #31
indianajo is offline indianajo  United States
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speaker relay connections often get high resistance in their old age. Peavey relays are better than average, but worth a check. Check the voltage across with the amp putting power in a 8 ohm resistor or something, ie the volume up. These big amps should drive a 6 ohm tea boiler okay. Use an ANALOG meter, DVM average over 2-4 seconds and smooth out the bumps to nothing. $29 5000ohm/volt meter from hardware store okay for those tests as long as has a 10 v scale.
On the bose check the DC voltage at the input to the protection relay. If over about 200 mv there is a problem in the amp circuit. Must trace DC back to origin. I found in the PV-1.3k the input op amp had a bad solder joint to the minus pin, worked sometimes, sometimes put output at 180 vdc. I think 4 techs had been in there since 1993 and not found that. Had a label on the speaker terminal "DO NOT USE CHANNEL A". Poking bad solder joints with a plastic stick helps. Also a meter probe.
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Last edited by indianajo; 13th November 2019 at 08:04 PM.
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Old 13th November 2019, 09:33 PM   #32
StewartH83 is offline StewartH83  England
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Again, fantastic guidance. I'm sure I can handle doing that in the morning. Your a superb help, can't thank you enough. I'll also look for an anolog meter too. I heard previously they are more precise so I think it will be a great tool for the future. I'll get a scope and a signal generator when I get Christmas out the way.
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Old 14th November 2019, 04:24 PM   #33
StewartH83 is offline StewartH83  England
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I found a problem on the Bose while going over the service manual and going through the amp before taking it apart. One of the big filter caps has a burnt screw and burn marks on the board around the screw. Only one of the four 22,000uF caps has the issue on its negative terminal. I guess it's a clue to what's gone wrong and probably a screwed capacitor. Is it likely something before the caps has gone causing the damage?
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Old 14th November 2019, 04:27 PM   #34
StewartH83 is offline StewartH83  England
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Sorry, not the best images of it as its tight
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Old 14th November 2019, 07:49 PM   #35
indianajo is offline indianajo  United States
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Electrolytic caps are the time fuses of electronics. The production engineers & marketing pick a time they want the amp to blow up. Some brands 1 year, some brands 20 years. Then they buy that quality electrolytic capacitors. Epoxy sealed capacitors were made in the 70's that would contain the water "forever". Nobody but Fender & some medical suppliers used them. Ask a guitar amp repairman about green CDE capacitors from the 70's.
The big question, is the transformer or rectifier damaged? Before buying $80 in caps (and screw terminal caps aren't cheap) you need to load the transformer with a 8 ohm 600 w tea boiler or log resistor. Then plug in, make some heat, read the value of the AC coming in from the light bulb box. 80% or lower of wall voltage, your transformer may have a shorted turn. Use an alligator clip to read voltage over 25, from one hand to the other it can stop your heart. No jewelry on hands or neck.
Rectifiers can be measured with the transformer unsoldered. .55 to .75 v forwards, ---- or 9999 backwards on diode scale.
BTW when shopping for scope, make sure it will cover these high voltage amps you work on. Many inexpensive ones only go to +- 60 vdc. Then there are the x10 and x100 probes, which are not cheap if you step one.
Just replaced ALL the e-caps in a farnell brand "Stellar Labs" HDTV converter DT400. 8 years and started hanging up & rebooting. Back to new performance. Getting ready to put all new e-caps in a Compaq 14" CRT display that lasted 15 years. Still works for 10 minutes before the horizontal circuit messes up. Using that to replace the Samsung 32" LED tv that lasted 23 months before quitting. Model UN323400DBF if anybody is thinking buying one of those pieces of instant garbage.
BTW when putting in new e-caps, try to buy the longest service life available. 3000 hours @ 85 C typically for 3300 uf up, smaller ones 10000 hours @ 105 C. Farnell & digikey will show you in the selector table if you ask, Mouser makes you download each datasheet & read it. Don't know what RS does. I have no contact with the German distributors. Brands to respect Nichicon, Rubicon, Panasonic, Vishay. 2nd tier CDE, United Chemicon, multicomp (farnell house brand). Some houses won't tell you what brand & part # cap they are selling. Stay away; I got average 8 years out of TV parts store e-caps before the debit card was invented.
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Last edited by indianajo; 14th November 2019 at 08:03 PM.
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Old 15th November 2019, 07:52 AM   #36
StewartH83 is offline StewartH83  England
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I'm learning so much from you and confirms some of knowledge I've learnt in the last 12 months too, especially about the capacitor brands and history. I like the Panasonic (FR mainly) and Nichicon (PS/PW) for power supplies and standard Nichicon/Nippon for signal paths. I feel the Japanese caps are my favourite yet won't mind using Vishay or Epcos neither. I will struggle getting the same sized Nippons like these. I've found some same brand wider and less taller ones in Ireland with one value higher voltage, which I'd prefer, yet that means I'd have to move and remount them running a wire with them ring connectors I'd think. If I have to move them it opens other brands options up and RS Components (which one is walking distance from my home) have good options and prices on this size.

Before I buy anything I'll get the PSU out, check the rectifiers properly then check the transformer like you kindly explained well. We call a tea boiler a kettle over here and never seen one below 2,000watts, our mains voltage is higher I guess. I'm surprised you use an electric tea boiler, I thought Americans just use stove ones that whistle. I like both.

I also noticed another 22k cap negative terminal has white marks like heat marks.

Great advice on the scope, no doubt I'll come back to this thread before I buy it to make sure, like other things.

I like how you improved the reliability and fixed your TVs. I did the PSUs in my LG and Panasonic TV recently with good caps. Also fixed the PSUs in my washing machine and electric shower, replaced Capxon caps with Panasonic, unbelievable improvements, my washer is louder than before it broke now to say the least lol

I'll take a look at both amps later today, I recapped a 90s Pioneer amp last night, the DBT takes away nerves as well ha
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