I Have a Peavey UMA 752 mixer amp with the SPS light on all the time. When I got it the outputs were shorted and I replaced them and didn't find anything else wrong. It will reproduce a clean sine wave. The SPS light is on all the time and the clip light doesn't come on when the output is clipped. I don't have a schematic so any help would be much appreciated.
All the inputs work fine and will show a overloaded or clipped input and they will mute as set up.
All the inputs work fine and will show a overloaded or clipped input and they will mute as set up.
Hey, wait until some people actually has the chance to *read* your question 🙂
As suggested above, *start* by asking Peavey for the schematic and posting it here.
Without it, just an educated guess:
Well, probably there still is something else wrong.
Which probably means there is DC at the output and it triggers speaker protection system.
Based on what it does, it must be a conventional amplifier , 75W into 4 ohm, with an added autotransformer to provide for the 8 ohm and voltage speaker outs.
If so, it will be hard to detect DC at the output because transformer primary has very low DC resistance, think tenths of ohms.
I would confirm it´s effectively built that way, diconnect the OT and check for DC at the output.
If present (I guess it is), continue troubleshooting the conventional amplifier before reattaching the OT.
Where? 😕
Speaker out? Preamp out? On some board terminal but not on a speaker?
Is there any speaker out relay involved?
Is there any connector you pulled and forgot to reinsert?
How do you know it clips?
How do you know? Where are you measuring/scoping?
In any case, I guess you have a power amp problem, for now wouldn´t worry about the preamp, beyond checking it works at all.
Before Peavey was bought up by Harman schematics were easy to get. The company I retired from was always able to secure a schematic for me.
The DC present in the amp is in the MV range which indicates its working correctly. The output of the amp is connected to a 4 ohm dummy load along with the scope and RMS volt meter. The sine wave is clean. So, in my opinion the power amp is working correctly. The monitoring circuit the SPS and clip indicators are not working correctly.
Dispite having worked for a sound contractor for 25+ years and retiring I am unable to secure a schematic from Peavey like I used to be able before Harman bought them out. Harman's idea of help is to contact their repair center and send it in. I've repaired their products for over 25 years.
Nothing I forgot to plug in or plugged in incorrectly.
The DC present in the amp is in the MV range which indicates its working correctly. The output of the amp is connected to a 4 ohm dummy load along with the scope and RMS volt meter. The sine wave is clean. So, in my opinion the power amp is working correctly. The monitoring circuit the SPS and clip indicators are not working correctly.
Dispite having worked for a sound contractor for 25+ years and retiring I am unable to secure a schematic from Peavey like I used to be able before Harman bought them out. Harman's idea of help is to contact their repair center and send it in. I've repaired their products for over 25 years.
Nothing I forgot to plug in or plugged in incorrectly.
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Several pictures
Bottom view
The outputs and emitter resistors have been replaced. All semiconductors tested.
Top view
J8 Fan, J4 output, P1, P2, P3 supply. J5 low voltage supply. J1 connection to the front board.
Need to know U1 and U10 function with respect to amplifier operation.
Bottom view
The outputs and emitter resistors have been replaced. All semiconductors tested.
Top view
J8 Fan, J4 output, P1, P2, P3 supply. J5 low voltage supply. J1 connection to the front board.
Need to know U1 and U10 function with respect to amplifier operation.
Attachments
Don't know the exact date but did find the following:
Competition for Harman_International_Industries (HAR)
Stock:Harman International Industries (HAR)...
Harman International Industries (HAR ... market include the Electro Voice division of ... products include Yamaha, Peavey, Rane ...
With respect to the mixeramp.......
Pulled the board for pictures, put it back together, same connectors same place ( cannot connect it wrong) it works no SPS light on until it clips now.
Don't know why but it will go to someone in need now. SPS works properly, no clip light, don't know what I was thinking too many amps on my bench at the same time that I'm working on.
Everytime Harman takes on another company the customer service goes down the drain along with the ability to obtain free schematics.
It would seem now that Harman has been purchased by Samsung.
Competition for Harman_International_Industries (HAR)
Stock:Harman International Industries (HAR)...
Harman International Industries (HAR ... market include the Electro Voice division of ... products include Yamaha, Peavey, Rane ...
With respect to the mixeramp.......
Pulled the board for pictures, put it back together, same connectors same place ( cannot connect it wrong) it works no SPS light on until it clips now.
Don't know why but it will go to someone in need now. SPS works properly, no clip light, don't know what I was thinking too many amps on my bench at the same time that I'm working on.
Everytime Harman takes on another company the customer service goes down the drain along with the ability to obtain free schematics.
It would seem now that Harman has been purchased by Samsung.
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Usually Enzo drops in and he has worked on everything PA or instrument, he knows way more than me. But he does take time out for trips occasionally.
Well, since SPS means speaker protection circuit, I'd lift one leg of the 7 v diac (sbs) Pcavey typically used to see if it still drops 7 v. I tested mine with a 12 v power supply and a 10k resistor in series. It was shorted on one channel of my amp. In the age of microprocessors that function may have moved to that part.
In the clip detect I lost both the op amp and a jfet. When the output transistors go a lot of parts get damaged by the rail voltage coming out the base lines. Okay for amateurs to fix, not very economic for pros.
Sorry to hear about the end of Peavey, last of the US entertainmnt industry with factories and a parts department.
Well, since SPS means speaker protection circuit, I'd lift one leg of the 7 v diac (sbs) Pcavey typically used to see if it still drops 7 v. I tested mine with a 12 v power supply and a 10k resistor in series. It was shorted on one channel of my amp. In the age of microprocessors that function may have moved to that part.
In the clip detect I lost both the op amp and a jfet. When the output transistors go a lot of parts get damaged by the rail voltage coming out the base lines. Okay for amateurs to fix, not very economic for pros.
Sorry to hear about the end of Peavey, last of the US entertainmnt industry with factories and a parts department.
Glad you solved it. 🙂
And it looks like it was a connector problem after all.
No need for them to be plugged the wrong way, sometimes the action of pulling and reinserting scratches grime/corrosion and makes contact good again or vibration had pulled one slightly away and reinserting them with authority again solves the problem.
Hope new users will be happy with it 🙂
As of an overflowing bench .... same here 🙁
I spent weekend repairing some so at least I can see the wooden surface now 😉
And it looks like it was a connector problem after all.
No need for them to be plugged the wrong way, sometimes the action of pulling and reinserting scratches grime/corrosion and makes contact good again or vibration had pulled one slightly away and reinserting them with authority again solves the problem.
Hope new users will be happy with it 🙂
As of an overflowing bench .... same here 🙁
I spent weekend repairing some so at least I can see the wooden surface now 😉
Please note the keyword highlighted above - Peavey is just one if its competitors, not a subsidiary. Peavey remains a family-owned business.
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