Ultra 112 Ch. Switching Nightmare.....

[abav]

Good Afternoon. I have a Ultra 112 that apparently was hit by 220. After replacing fuses and bringing her up with a variac.... everything looked good except for the channel switching. I know that the crunch channel does not operate without the fs, and here is where it goes downhill!!
The fs is a 3 button with red ultra led, yellow lead led on the first button, middle button has a green bypass, and last button is a red effects led. I cant get the crunch to operate...The lead yellow led is operating the ultra channel, and when switched to ultra red, i get very little distortion, but still controlled by the ultra channel. I have all the j-fets/mac xstr. and replaced them to no avail. I did notice that the connector pins on the breakaway board (501-503) were soldered together..unlike what the schematic diagram showed....so i reversed that. When i emailed peavey...The parts department said that was the wrong fs and it needs rewired....However, when i called to verify it....They said it was the correct fs. If anyone can give me some advise or direction while i clear my head...That would be GREATLY appreciated.

Thank you for your time

Art

[abav]

Oh.. BTW....The lady who owns the amp told me that a electrician wired the outlets wrong and they were 220 instead of 110...(oops!!).
I had to repair a couple of other amps for her...(that's the reason for the 220 reference in the original thread)

[Euthymia]

I'd start by checking the low voltage power supplies. That kind of switching is usually run on 5 to 15VDC.

You'll likely find a blown up voltage regulator and/or blown up zener.

[Enzo]

It's relays.

Does the channel switching all work WITHOUT the FS? I know you can;t get Crunch that way, but do the panel buttons all do what they should? Do they click the relays on and off even if you can't listen to the channel?

The relays run on the +24v rail. The channel switching relays are on the bottom of the power supply page - page 3 if you have the whole set pdf. All the FS does is ground the low end of each relay. Well some are pairs of relays in series. And of course for the FS to work properly the panel switches have to be in the proper position.

[abav]

Yes Enzo, w/o the fs, the front panel buttons work. The channel button under the brightness button switches from clean to the ultra channel...and the ultra button gives more distortion. I do hear the relay click when the channel button is depressed.

The 24v rail is fine. I checked all the diodes across the relays( lifting one end to make sure)...and they are ok. The voltage on the clamping j-fets drops from 24v then back up within a second when a fs button is depressed.

Is a relay supposed to click when using the fs between lead and ultra??..(none right now).

Im thinking maybe a bad relay (k3)?? Thanks again for your helpful insight.

[Enzo]

Look at the schematic. There are relays all connected to the +24 ultimately. In some cases there ar two in series, and otherwise a single one with a resistor in series. All the low ends of these relay coils run out to the FS jack. Grounding those points should energize the particular relay(s). A real simple test is this: is there +24VDC on each FS jack pin that goes to a relay? If not, the relay coil is open, or the path to it. DOn't be confused by the LED voltages fed through those resistors.

For that matter, you have the diode across each relay coil. Leave the diode in circuit, and measure resistance across it. SInce it is in parallel with the relay coil, you are measuring the coil resistance. Open or not.

[abav]

Well enzo (or anyone), i have verified the voltages on pins 5-6-7 of the 7 pin din plug ....and can manually short them to ground, engaging the relays!! The amp works fine !! The damn fs needs rewired. I have emailed peavey about a diagram for the footswitch, however, there has been no reply. Would anyone happen to have a diagram for the 3 button fs for a ultra??

This is one of those repairs when the 'Mother' tells you..."everything worked fine"....and you cant tell her otherwise!! Thank god this doesnt happen all the time...or i would need a bottle of 'Crown' on my bench!!

Well thats what happens when you 'assume'...LOL

Thanks again.....

Art

[Enzo]

Look at the schematic, pin 4 is ground and pins 5,6,7 are the control lines. You ground a control line to activate it. I'd verify the FS cable has integrity, then make sure to wire a common to the three switches to pin 4 and each switch hot side as appropriate to pins 5,6,7.

[abav]

Ok, i got the Pdf for the footswitch today and it needed rewired. Just got it done....works fine. Thank you Enzo for all of your help !!

[cgoepel]

Enzo,
Thanks for your knowledge on the switching scheme on this amp. I'm a repair tech and couldn't get channel 2 operational. Looking at the schematic sent me into tailspins. The designer probably did this to keep any amp copykats scratching their heads. My customer (a music store) didn't have the footswitch and I thought I could troubleshoot the schematic on basic principals and following the schematic -wrong. Your knowledge of the footswitch function saved the day. Thank you very much. Charlie G.