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Discussion Starter · #1 ·
So I'm worried after my tinkering with inputs and outputs and multiple effects loops and units recently that I may have screwed something up in my Peavey ValveKing 112 preamp section, or maybe just a tube. If I play the guitar into the input (either the high or low) of the Peavey, I get no sound out of the speaker (but you can hear it very faintly in there somewhere). If I connect my blackstar amps preamp section into the return on the Peavey, it comes through as it should.

I have it set up like this:

Guitar - Blackstar (in) - Blackstar(send) - POD (guitar in) - POD (Left out) - Blackstar (return) - POD (Right out) - Peavey Valveking return.

This works properly with the Blackstar acting (I believe....correct me if I'm mistaken), as the preamp to both power sections of each amplifier via the loop.

I will most likely take it in to get checked and repaired, but I would really really appreciate any help or experience that some of you here may have with amplifiers. I like to know what I'm dealing with before forking over money to a repair guy. I don't go on blind faith often.

Thanks to anyone in advance, and I will of course be watching this thread very closely.
 

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Often send and return jacks include a mechanical switch that cuts a signal path so the signal is re-routed through the external effect(s).

e.g. your preamp send jack might have a switch that disables the standard (internal) signal path from the preamp to the power amp whenever a cable is inserted.

I'd definitely check your jacks first. They might be dirty, or the mechanical switch might be bent and no longer springing back into place to make contact when the cable is removed.
 

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Discussion Starter · #7 · (Edited)
Thanks for this guys. I'll respond to a couple of things in order here.

@ dtsaudio. The issue is with the guitar input jack, both of them (high and low), on the amp. It's also the first time I've used the low input ever, so not likley a broken or dirty jack (s). I also just use this amp at home, so it isn't a working musicians workhorse type of deal. Basically stays plugged in in my music room without moving around. I definitely will inspect both of course.

@ Amagras. Thanks for confirming (sorta?) that the input is part of the preamp section and the Loop send/return is the power section. That is what I understood it to be as well.

@ Greg Ellis. There is no switch there. I think it's internally switched or something

@nonreverb. Tried the short cable to connect the send/return idea out already. No luck there.

I did do a little troubleshooting research on that Tech dude.....Mr. Google. So I did try a couple of different things to test before posting here.

Thanks for the suggestions so far guys. Also, from what I understand, it wouldn't be the main fuse (which I checked anyways), because from what I understand I wouldn't have any power indicator lights on if it was that.

Is there a possibility of it being the preamp tube(s)? There are 3 preamp AX7's and 2 Power amp 6L6's. Oh, I also checked the obvious, neither the clean nor dirty channels work.
 

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Yes, there is a chance it could be a preamp tube. Not the one closest to the power tubes though, it is after the FX return jack so it must be working.
Are the 2 preamp tubes closest to the front lit up?
Try swapping them with some known good tubes.
 

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Discussion Starter · #9 ·
Yes, there is a chance it could be a preamp tube. Not the one closest to the power tubes though, it is after the FX return jack so it must be working.
Are the 2 preamp tubes closest to the front lit up?
Try swapping them with some known good tubes.
Thanks for that. I'll check that out when I get a chance later. I had a cursory glance at the tubes when I was troubleshooting before, but not a good enough look for my preferences. I do not have any known working preamp tubes unfortunately. Any suggestions if it comes to that. I have 2 6L6 Groove tubes in the power section, but all the original preamps are the 12ax7's (Ruby) that came with the amplifier.
 

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Discussion Starter · #11 · (Edited)
Are the preamp tubes all lighting up?
Haven't been able to get at the amp yet, will be checking tonight.

EDIT: Just checked. 2 of the tubes (closest to the front of the amp) are pitch black, like how much more black can you get? And the answer is "None......none more black".

The preamp tube closest to the back of the amp has a very faint glow in 1 filament it looks like. The 2 Power tubes have 2 filaments lit up like Christmas lights.

I read that in certain amps (not sure about this one), that there could be an internal fuse that controls DC voltage to the preamp section that could be blown. The fuse that I removed was an external one.

If someone needs any more info to help, let me know please. I'm just getting into diddling around with tube amps so I really don't know allot about the inner workings yet. But I do have a background in electronics (that wasn't used to its fullest potential :))....so I understand the basic laws and theories regarding Ohms, Wattage, Voltage, resistance, impedance etc....
 

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The preamp tube close to the back is working, otherwise the power amp section would not work when using the FX return with the blackstar or Pod.
Your fault seems to be a bad connection to the heaters of V1 & V2 preamp tubes.
You said you would probably take it in for repair but I'll run it down anyway.

Lethal voltages are present in the amp so if you are not aware of the safety procedures, do not open the amp.

The bad connection is probably a solder joint on the V1 or V2 sockets.
There will be 6V DC at pin9 of V3 (the rearmost preamp tube). From there that 6V should also connect to pin9 of V1 and pin9 of V2. It is probably not making it there. Or the bad connection may be between V1 pins 4&5/V2 pins 4&5 and ground.
Heater circuits are shown on page 10 of schematic available here (wait till "processing" changes to "get manual") :
http://elektrotanya.com/peavey_valveking_50_112.pdf/download.html
 

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Discussion Starter · #13 ·
The preamp tube close to the back is working, otherwise the power amp section would not work when using the FX return with the blackstar or Pod.
Your fault seems to be a bad connection to the heaters of V1 & V2 preamp tubes.
You said you would probably take it in for repair but I'll run it down anyway.

Lethal voltages are present in the amp so if you are not aware of the safety procedures, do not open the amp.

The bad connection is probably a solder joint on the V1 or V2 sockets.
There will be 6V DC at pin9 of V3 (the rearmost preamp tube). From there that 6V should also connect to pin9 of V1 and pin9 of V2. It is probably not making it there. Or the bad connection may be between V1 pins 4&5/V2 pins 4&5 and ground.
Heater circuits are shown on page 10 of schematic available here (wait till "processing" changes to "get manual") :
http://elektrotanya.com/peavey_valveking_50_112.pdf/download.html

Thanks JBwelder. I've read a number of your other posts and I'm very comfortable with your opinion on amplifiers. I suspected it may be a little more than just the tubes. Didn't make sense for all the tubes to just "go" at once. I'm well aware of the capacitance issue with amplifiers and televisions, but I'm reticent to attempt that type of fix. If it was as simple as just changing a tube, no problems. But that's a pile of dung I don't feel comfortable with at the moment. I will be taking the amp in to the local L&M (they have an amp guy who works as a sub contractor to them here in Edmonton, who I've dealt with before and am happy with). Thank you so much for taking the time to help out with this. I'll update the thread at a later date, hopefully with some specifics. I might just take it into "the guy" himself....can't remember his name at the moment.

Thanks again.
 

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The Peavey's (at least some) use series heater circuits.The Valveking has rectified DC heaters and might have separate series heater circuits for the preamp board and power boards. If that's the case, replacing V1 and/or V2 just might do the trick....
 

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Looking at the schematic, V1, V2 filaments are actually in parallel. They are the only tubes like that. The rest have their filaments in series. So it's possible fro those two to be out and rest lit.
Check board connections, and also the push connectors from the transformer. You'll need to trace through the circuit. Filament voltage will appear on pin 9 Pin 4&5 are ground.
 

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Discussion Starter · #16 ·
The Peavey's (at least some) use series heater circuits.The Valveking has rectified DC heaters and might have separate series heater circuits for the preamp board and power boards. If that's the case, replacing V1 and/or V2 just might do the trick....
Looking at the schematic, V1, V2 filaments are actually in parallel. They are the only tubes like that. The rest have their filaments in series. So it's possible fro those two to be out and rest lit.
Check board connections, and also the push connectors from the transformer. You'll need to trace through the circuit. Filament voltage will appear on pin 9 Pin 4&5 are ground.
Great stuff guys. I read on another sight much like this one that checking the rectified DC heater (which I believe required the amp chassis to be removed), to possibly have an issue or be part of it. I was also wondering if the tubes themselves were in series, as what I stated earlier in this thread (it didn't make sense for all the tubes to blow at once), would actually happen if they were in series. So thanks much for clearing that up for me on all your own time. I've unfortunately been a bit busy lately and didn't even read the schematic that was so kindly linked by jbwelder. My bad.

Just so you guys know, I've also read a number of all of your posts and was hoping dudes like you would respond. Practical experience goes a very long way in my books, so I really appreciate your help. Keep any more ideas coming folks, the more ideas the better. As long as they don't take away from the issue at hand!
 

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Discussion Starter · #17 ·
So a question. Since I noticed the 1 filament very dimly lit on V3, is that normal for a pre amp tube? I was thinking it should be way brighter than that (considering the power tubes are so bright).

Definitely makes sense that V1 and V2 may not both be blown if in series. I still have to wrap my head around some of the other posts here again after finally getting a chance to look at what's happening with the schematic.
 

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vkhtrs.jpg

V1 & V2 are in parallel, not series. So it must be a connection common to both for them both to be out.
One side of their heaters goes to ground, the other side goes to a 6V feed from V3 (labelled 6V1 on schem).
V3 is definitely working correctly as it is after the FX return jack, which you reported works as it should (power amp section). We also therefore know all points in the heater circuit of V3,V4, and V5 are working.
So this 6V feed must be working, just not getting to V1/V2. Or, it is getting there but their common ground connection is bad.
 

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Discussion Starter · #19 ·
So to get this right, both V1 and V2 are out, which either means that both are toast, because if 1 was still working then it would still be getting the 6V feed, which is obviously working because V3, which is connected to the Power tubes, is working, and V3 is feeding them the 6V supply. OR the common ground between V1 and V2 of the pre amp section is a bust.

I had to sprinkle in a few of my own electronics terms in there just to get it straight. :D
 

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So to get this right, both V1 and V2 are out, which either means that both are toast, because if 1 was still working then it would still be getting the 6V feed, which is obviously working because V3, which is connected to the Power tubes, is working, and V3 is feeding them the 6V supply. OR the common ground between V1 and V2 of the pre amp section is a bust.

I had to sprinkle in a few of my own electronics terms in there just to get it straight. :D
Correct...or the supply voltage isn't getting to V1/V2.
 
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