Fender Hot Ros Deluxe -clean channel not working

[Lastnote]

LastNote
Amp had a loose filter cap, replaced all 22uf cap (not 47uf it was good and no leaks).
Put the amp together clean channel not working, dirty channel is good. LED indicator light is off when selector button is up and yellow when push in no red indicator light. Master vol working when selector button is push in position, vol does not work in any selector position. Tested all resistor on the small tube ckt board: R38,39,40, 41,42,43, 44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62 ,64,65,66,67,68,69,80,81 all test good. 5 Watt resistor R78 & 79 good at both end 48v in 16 v out. Voltage out of CR13 & 14 good at 16v—Any ideas

[Jazz P Bass]

Check the multi color LED and the soldering.
It may have gotten bumped loose when manhandling the board.
It needs that LED for the switching to function properly.

[52 Bill]

Master vol working when selector button is push in position, vol does not work in any selector position.

There are two relays that control the clean and distortion control modes. If the Distortion Master works when the Dist. channel is selected, then you know that relay K2 is closing. Does the Distortion Drive control work? If it does then relay K1 is working. That doesn't mean that the relays are okay, but at least you know that the relay control circuitry is working.

The schematic has a list of test points for the switching circuitry and what voltages should be when in each of the three channel modes. Try checking these test points. If the red more drive mode is missing test the voltages at TP36 (pin 1 of U3). It should swing to +16 volts when the more drive switch is turned on.

When you had the board out, did you visually check the solder connections around the jacks and the pots? These are a common area for broken and cold solder connections.

[Drewline]

Check solder around the volume pot. It is active only in the clean mode. It is very easy to bend or break a lead on the LED when reinstalling the PCB into the chassis. We get a fair number of these amps where someone has tried to work on it. Bad traces, bad solder. Also check the ribon connectors.

[Lastnote]

LastNote,

First of all thank you all very much for pitching in and helping me out!
I replaced the K1 and no cigar. Will check the LED and vol pot solder joints, Red LED is working and I will take voltage reading at all TPs tomorrow.

Again thank you all,

Lastnote

[Lastnote]

LastNote:
Sorry guys for taking so long to respond. I couldn't do the TP level check, because I have an arching problem at jumper cable P4A where it connects to the main CB. It is arching to the trace going to the bias adjust pot. I replaced the ribbon cable P4 (had to cut off 2 wire section form the 6 wire ribbon cable) and C4 & C5 diodes (though they tested well) hoping that would fix the problem. When put the amp stand-by switch on, it arched again. I checked everything again and I found that the trace going to the bias pot was exposed right next to P4A solder point. I cleaned between the solder point and the trace. I applied liquid tape on the trace and the solder point. I also found R76 was fried, I replaced it too. I don’t know if the arching caused R76 to fail or the failure of R76 cased the arching. I have not tested the amp after I made these repairs; will wait for your replies. I found the jumper cable on line at Darren Riley’s Guitar & Amp Shop, part number: Fender Ribbon cable JMPR 6 CKT .156 RDU 0050687000.

Thank you in advance!

[52 Bill]

I don’t know if the arching caused R76 to fail or the failure of R76 cased the arching. I have not tested the amp after I made these repairs; will wait for your replies.

I've not seen any arcing in these before, but anything can happen. R76 is part of the bias voltage supply and could have been damaged by the arcing. If there was any burned traces, you need to cut away all of the carbonized areas or it will continue to arc.

[Lastnote]

LastNote:

Tks 52 Bill,

That is what I did and I coated the trace with liquid electrical tape. I will test the amp today, now that I made those repairs.
Talk to you soon.

LastNote

[Lastnote]

52 Bill

The problem still exist, arching at the P4 cable two wire flat cable (right cable strand) on tube CB. I have to back off, put on my thinking cap and try to figure this problem out. Any help from the forum will be greatly appreciated. I did not have this problem when I first started to replace the filter caps. This developed after I put the chassis back together.

Alexx

LastNote

[g1]

Any chance the ribbon cable is broken or cracked? Or the trace is leads to is cracked?

[52 Bill]

The problem still exist, arching at the P4 cable two wire flat cable (right cable strand) on tube CB. I have to back off, put on my thinking cap and try to figure this problem out.

The P4 cable connects the high voltage B+ to the screen grid resistors and also connects the output tube cathode bias network to ground.

Exactly what is arcing? Are the two wires in the cable shorting together or? Which side is it the tube board side or the main pc board side?

You may need to run a separate insulated wire to supply the screen grids.

Edit: Okay I read that it is on the main pc board side. If you can't clean up the board enough, you will need to cut the high voltage trace away from the damaged area and route it away to the tube board via a separate wire.

[Lastnote]

LastNote, 12/17/2014
1-To re-cap the original problem: Amp made cracking noise when played hard or low bass notes.
2-Found bad C33 (lose on it's axial lead) and ,C35, C36 were leaking; Replaced all three 22uf filter caps
3-I put the amp together; Clean channel is attenuated to a faint sound, Dirty channel working fine, switching is working fine.
4-I checked the signal path with 1000hz audio tone into guitar input jack #1. I got as far as K1, no signal beyond K1-I replaced K1-No change
5-In the process of moving the CBs, I broke a wire in the 6 wire flat ribbon cable to V1 and the a wire in the 2 wire flat ribbon cable to V4.
6-I replaced both ribbon cables (with fender original cables)
7-However, P4 2 wire cable began to arch on the small CB @ the base of V4 power tube support column.
8-I cleaned the CB and applied liquid electrical tape-No more arching.
9-The arching problem is re-solved, however R61 gets so hot.
10-I now have: Clean channel is attenuated to a faint sound, Dirty channel working fine, switching is working fine, plus the R61 problem.
Note:
1. I had this amp in my shop before, it had R61,CR4 and R64 fried and the pad for R61 gone, I had to put some jumper wire.
2. I made the repair and the amp worked well until the filter cap problem.
3. Filament voltage to all tubes is good. However, V1 & V2 tubes do not get hot, not even warm?
4. I am not 100% certain, but I think moving the CBs in and out case something to get lose that I can't see or find.
LastNote

[g1]

Not sure if the arcing is responsible for the R61 problem, it's possible. However R61 (or R62) overheating is usually a pretty good indication of a defective power tube.
As far as the normal channel issue, on the left side of the schematic is a listing of all voltages for the channel switching circuits. Make sure all the correct conditions are met for clean setting voltages at the TP's listed.

[Lastnote]

g-one,

Arching issue is fixed, by cleaning the CB and coating area with liquid electrical tape. All the power tubes and pre-amp tubes are new and I tested the power tubes with my maxi-matcher 2 tester. I have Elecitro Harmonic 6L6EH in the amp, going to check the current draw today to insure it is not to much for this amp, previously I used JJ 6L6GC. Any ideal on the cold V1 & V2 preamp tubes? Will start to check TP voltage once I get this amp stabilized.
Thank so very much for your advise!

LastNote

[52 Bill]

If R61 gets hot even with a new tube, check the tube pc board for shorted traces, solder bridges and check the tube socket for carbon arcing.

If the filament voltages are okay at the sockets of v1 and v2 check for high voltage at test points TP2, TP5, TP8, etc. And check for voltages at the cathodes TP3, TP6, etc.

Go back and recheck your earlier work, also recheck all of the jumper wires between the two boards. Personally, I try not to pull any of the transformer connectors when pulling the boards, but if you did pull any are you sure that they have all been put back correctly and are making good contacts?