Fender Roc Pro 1000 - Output is SUPER low

[slow6i]

Hey all! Ive been reading on the forums for a couple days now trying to figure out how to fix my amp, but alas, it has come time that I must post.

Amp is a fender roc pro 1000 combo. When I got it, I had a problem with the foot switch only switching between clean and the yellow distortion channel. So, me being me, I opened it up, and resoldered all of the contacts on the board. However, I accidentally bridged one -- in all of my infinite skill -- and obviously broke something because of that. When I powered on, there was no smoke, so thats good, but now Im trying to find the components that need to be replaced and Im hoping you all can help me.

Here is what I know:

- Amp has low output. Volumes all the way up, and I have to be sitting right next to it to hear it.
- Channel switching works with the face plate controls perfectly fine.
- Both clean and distortion work at this lower output.
- At TP22, I am getting ~30VAC, at TP23 I am getting ~80VAC (thats twice what it should be according to the schematic.)
- I was stupid and careless and torched my amp
- I want to fix it if possible.

So... Is there hope? Or should I scrap it and buy a different amp?

Thanks!

[nickb]

Welcome! You're not the first to make a mistake and I'm sure it can be fixed.

In order to measure tp23 you must put your meter on the DCV range, not ACV.

To fix this we will need to have a means of generating a test signal and then tracing it signal through the amp. So, what test equipment do you have?

Schematic
Roc_Pro_1000_schematic.pdf

[slow6i]

Welcome! You're not the first to make a mistake and I'm sure it can be fixed.

In order to measure tp23 you must put your meter on the DCV range, not ACV.

To fix this we will need to have a means of generating a test signal and then tracing it signal through the amp. So, what test equipment do you have?

Well, now that you say that, of course it needs to be measured in dcv... *derp*

Anyway, as far as test equipment goes, I really only have my volt meter. By signal, I assume that you are talking about an input signal from something like a guitar or keyboard or the like? Could I use my PC as an input with a tone generated by audacity or something?

My circuits experience is limited, especially diagnostics, so please bear with me. To me, its more worth it to diagnose and replace cheap parts myself, regardless of how long it takes then to take it to a shop and have them fix it. I don't learn anything that way.

[glebert]

I usually try to first figure out if it is a preamp or a power amp problem. Do you have another amp that has either an effects loop or a pre amp out / power amp in? A mixing board or mic preamp can also work if you have 1/4" outs. If you can use a known good preamp into the effects loop Return you can see if the power amp is working ok, and vice versa test the preamp by lining out of of the Send into an amp or mixer to see if you have a strong signal there. For testing the power amp you want to turn the effects mix all the way up.

Also, a smartphone with a function generator app can make a good test signal generator, but if you don't have a good meter or an oscilloscope it may not help that much. I am lucky to have an oscilloscope, never tried my DMMs to track small signals.

[Enzo]

To test the power amp, you can just plug the guitar into the FX return or Power AMp In jack. To test the preamp out or FX send yes you will need another amp.

[slow6i]

I usually try to first figure out if it is a preamp or a power amp problem. Do you have another amp that has either an effects loop or a pre amp out / power amp in? A mixing board or mic preamp can also work if you have 1/4" outs. If you can use a known good preamp into the effects loop Return you can see if the power amp is working ok, and vice versa test the preamp by lining out of of the Send into an amp or mixer to see if you have a strong signal there. For testing the power amp you want to turn the effects mix all the way up.

Also, a smartphone with a function generator app can make a good test signal generator, but if you don't have a good meter or an oscilloscope it may not help that much. I am lucky to have an oscilloscope, never tried my DMMs to track small signals.

Portland, Or. Huh? I'm just across the river in Vancouver... anywho, I have a little Dean practice amp that has high and low inputs, and can go to an external speaker via 1/4 jack, but that's my only other guitar equipment. I will report back with results tomorrow evening.

[glebert]

Whatever you do don't put the Dean speaker output into the Roc Pro effects loop, that will blow it. You could probably get away with lining the Send from the Roc Pro to the Low input on the Dean but keep your volume on the Roc Pro way down at first as you don't want to blow the input on your working amp. Do what Enzo said and just plug a guitar into the Return jack on the Roc Pro and see if you get much sound out. Usually you don't get as much volume to the speaker when you do that, and since your problem is low volume it may be somewhat inconclusive, but worth a try.

You may want to probe the op amps and make sure they have correct voltages (+/-16V on pins 8 and 4 respectively), and one other test you can do is to touch the op amp input pins (2,3,5, or 6 depending on config) with your meter probe and see if you get a pop through the speaker. If the problem is in the preamp as you go through the signal chain eventually you should get louder pops once you get past the problem.

[glebert]

Also, with your original problem of it only switching between clean channel and yellow drive, are you sure you have the right footswitch for it? I have a Performer 1000 (same circuit as Roc Pro) and when I use a different (wrong) Fender footswitch I can only switch between clean and yellow. Correct footswitch should be a 3 button P/N 0064465000

[slow6i]

Also, with your original problem of it only switching between clean channel and yellow drive, are you sure you have the right footswitch for it? I have a Performer 1000 (same circuit as Roc Pro) and when I use a different (wrong) Fender footswitch I can only switch between clean and yellow. Correct footswitch should be a 3 button P/N 0064465000

Tonight:

- Plugged my guitar into the FX return; nothing at all with the volume all the way up on both the instrument, and the amp.
- Plugged the FX send from the Roc into the low input on the Dean amp. Nothing.
- Plugged my guitar into the Dean, both inputs work.
- Decided against plugging the line out from the Roc to the input of the Dean.
- Tested the above mentioned pins, and results can be found at : https://docs.google.com/spreadsheets...it?usp=sharing
-- U7 is a different chip, so I got some questionable results initially, but after looking at the datasheet and retesting, it seems to be ok.

The foot pedal I have is PN 040409, from what I can find it is the correct one, but alas, I reserve the right to be wrong...

Whats next gentlemen?

[glebert]

Nice spreadsheet, BTW. I wish I was half that organized. This was done with clean channel? Was the volume up at least somewhat? Interesting that the first op amp where you get a response is pin 6 of U5, and a loud squeal at that point. If you crank the volume or the EQ pots all the way up do you hear the background noise increase? Wonder if there is something going on with Q7. Did you have a cable plugged in while you were doing this? Maybe Q7 (and Q6 on the drive channel) mutes the signal when there is nothing plugged in? Kind of weird how that inhibit line is fed with the -16V being connected through the switchjack in either position.

[nickb]

When doing these 'pop' tests you need to have something plugged into the input jack in order to defeat the muting of the reverb and the signal path prior to U5. You have a similar problem when probing U4 pin 3 as the return jack shorts (most of) the return signal to ground. So, redo these tests with something plugged in.

In any case, given you hear things when touching U5 you I'd expect to get something when plugging into the return jack. Redo that test but try different settings of the level switch and effect mix pot, just in case.

[g1]

This amp has a parallel FX loop, so when you plug your guitar directly into the FX return, you have to turn the FX mix pot up to 10.

[slow6i]

This amp has a parallel FX loop, so when you plug your guitar directly into the FX return, you have to turn the FX mix pot up to 10.

Thank you for all the reply's, unfortunately, it will be over a week before I will be able to test these suggestions... Thanks for sticking with me!

[slow6i]

When doing these 'pop' tests you need to have something plugged into the input jack in order to defeat the muting of the reverb and the signal path prior to U5. You have a similar problem when probing U4 pin 3 as the return jack shorts (most of) the return signal to ground. So, redo these tests with something plugged in.

In any case, given you hear things when touching U5 you I'd expect to get something when plugging into the return jack. Redo that test but try different settings of the level switch and effect mix pot, just in case.

Alright! Back from my work trip and I was able to sit down, albeit for only a minute, with my amp.

After plugging my guitar in through the FX return, and making sure all volumes / mixes were up, I get my guitar through the FX return (needed to turn up the effects mix as suggested. I had it down because my reverb wasnt working.)

Ill try to get to the pop test tomorrow during a homework break. So what is this telling me? Power amp seems good?

[nickb]

Yes, power amp is good.