Amp Help Tech Question

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braintheory

Well-known member
So the other day I was in a bit of a hurry (had an appointment to go to) and was turning on my Naylor SD100 for a very quick run before leaving and accidentally put the speaker cable into one of the fx loop jacks rather than the speaker ones. I was like why is there no sound and quickly caught it after 10-20 seconds and turned the amp off. I then put it in the right place (speaker jack) and there was still no sound. All the tubes lit up, the power light lit up, fuses looked fine, even tried the tubes from it, same cables and guitar in my other amps and they’re all fine in the other amps, but for whatever reason I can’t get any sound out of the Naylor right now. Can anyone explain what could be wrong? Did I make a big mistake with accidentally plugging it in that fx loop briefly? I never had the volume on it set that high fwiw
 
Fuses can look fine but be electrically be open, especially slo blow.

Check all fuses out of the amp with a multimeter - all should be dead shorts. Anything that isn’t needs replaced.

If fuses check out, I’m not sure what other protection circuits he builds into his amps (if any).
 
glpg80 said:
Fuses can look fine but be electrically be open, especially slo blow.

Check all fuses out of the amp with a multimeter - all should be dead shorts. Anything that isn’t needs replaced.

If fuses check out, I’m not sure what other protection circuits he builds into his amps (if any).
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I do have a multi-meter. How exactly do I use it to check the fuses? Sorry, I’m very not tech savvy haha
 
I would go ahead and get replacement fuses regardless. I wouldn't think 10 or 20 seconds like that would cause damage to the amps circuitry but it could. Hopefully a fuse protected it or maybe a single screen grid resistor. I did this with my Splawn once and it took me a long time to figure it out. Several minutes anyway. Luckily nothing happened. Good luck.
 
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So according to the beep test the fast blow fuse was bad, but the slo blow one was fine. I used the other fast blow fuse from my Naylor SD60 that has the same mA and V rating, but still no sound... I thought about trying another slo blow in it just case (despite it testing good), but I don't think I have any right now that are the right ones
 
after you replaced the fuse I would check your power tubes. 10-15 seconds shouldnt kill your OT. A tube can be bad even lighting up. Then as said earlier check the screen resistors. If its the white ones they will look cooked and be pretty obvious that they are fried. **Edit I saw where you checked the tubes*** At this point I would take it out of the headshell and look to see if you see any obvious cooked components. If nothing is obvious its going to take some troubleshooting with a meter and at that point I would take it to a tech.
 
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braintheory said:
So according to the beep test the fast blow fuse was bad, but the slo blow one was fine. I used the other fast blow fuse from my Naylor SD60 that has the same mA and V rating, but still no sound... I thought about trying another slo blow in it just case (despite it testing good), but I don't think I have any right now that are the right ones
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Check the fuse you just put in to see if it’s blown as well. If so, you’ve got a short to ground somewhere. Either a bad power tube or something has happened protection wise such as a screen grid resistor going south mentioned earlier.

Seems like dumb luck this would happen - we have all been there at least once.

After you read the fuse we could probably help you diagnose it with high resolution pictures but it sounds like the best action is to send it to a tech.
 
Was your guitar connected to the amp and were you hitting the strings trying to hear a sound? That could cause a problem if you did that.

Try replacing your preamp tubes to see if that helps.

Look inside to see if anything is damaged as well.

Also did you re-check the new fuse you put in? Maybe it blew again meaning something is damaged for sure.
 
glpg80 said:
Check the fuse you just put in to see if it’s blown as well. If so, you’ve got a short to ground somewhere. Either a bad power tube or something has happened protection wise such as a screen grid resistor going south mentioned earlier.

Seems like dumb luck this would happen - we have all been there at least once.

After you read the fuse we could probably help you diagnose it with high resolution pictures but it sounds like the best action is to send it to a tech.
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That fuse is still fine according to the beep test. Will take out the chassis later and take some pics
 
Krull said:
Was your guitar connected to the amp and were you hitting the strings trying to hear a sound? That could cause a problem if you did that.

Try replacing your preamp tubes to see if that helps.

Look inside to see if anything is damaged as well.

Also did you re-check the new fuse you put in? Maybe it blew again meaning something is damaged for sure.
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The guitar was connected. Already tried replacing all the preamp tubes with ones I know are good. I re-checked that new fuse and it’s still good according to the beep test with my multimeter. Will take out the chassis and look inside later today
 
braintheory said:
The guitar was connected. Already tried replacing all the preamp tubes with ones I know are good. I re-checked that new fuse and it’s still good according to the beep test with my multimeter. Will take out the chassis and look inside later today
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If you weren't hitting the strings then your transformer is likely safe, if you were playing the guitar for 30 seconds it's likely a problem for the transformer.
Hopefully it's something else. I've done the same to a couple amps (no speaker) but I've been lucky, only a power tube blew. Good luck.
 
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Krull said:
If you weren't hitting the strings then your transformer is likely safe, if you were playing the guitar for 30 seconds it's likely a problem for the transformer.
Hopefully it's something else. I've done the same to a couple amps (no speaker) but I've been lucky, only a power tube blew. Good luck.
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One thing you can do is plug your bias meter in and watch the tube bias as you try and play and see what happens, if the OT is bad the bias will go ski high so you have to be careful to not smoke a power tube but that is another way to tell.
 
jasonP said:
One thing you can do is plug your bias meter in and watch the tube bias as you try and play and see what happens, if the OT is bad the bias will go ski high so you have to be careful to not smoke a power tube but that is another way to tell.
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Will check with my bias meter. Thanks! Sounds like will a need trip to my tech sadly… he’s not cheap
 
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Krull said:
If you weren't hitting the strings then your transformer is likely safe, if you were playing the guitar for 30 seconds it's likely a problem for the transformer.
Hopefully it's something else. I've done the same to a couple amps (no speaker) but I've been lucky, only a power tube blew. Good luck.
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I was playing it for maybe 5-10 seconds
 
Does the amp have an fx loop? If so try plugging your guitar straight in to the fx return and see if you get sound there
 
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