I have a very clean BF Princeton that worked great for years. During a gig the PT completely burned up. Smoke, and a sickly burnt marsh-mellow smell filled the club. Later when I got it on the bench, I discovered it had a 30 amp car fuse!! I had never checked it all the years I've had it.
I have a Laney lc15r valve amp and the power transformer gets so hot after around 40 minutes of use that i can only touch it for 2 to 3 seconds only. What might cause this to happen ? regards. .love your videos.
To Christopher: "A bad amp repairman???" In my country they don't even exist anymore. So for me this guy is great. At least he's trying and has very good results. Today you just buy new and that's it??? He's not dead after repairing all that HV stuff so i think he knows what he's doing. Yeah he could be more safe but so do so many thrill seakers doing all that stupid stuff like bungee jumps and sorts. Everybody's got their own style of doing stuff. Don't buy all yhe stuff they teach you in school.
When I was a kid (60s), if something didn't work, it was - take the tubes to the big tester at the drug store. So I thought that tubes failed, nothing inside. I didn't know what capacitors were for. Funny thing was, it often was the case, replace the bad tube, and it worked. Never was concerned that something caused a tube to fail. But I still check tubes first, usually indicates the problem area. Don
I think you erred when figuring dissipation. Aren't you supposed to subtract cathode voltage drop from plate voltage when figuring plate dissipation? You used cathode current times plate voltage for your calculations which gave you 9.77 watts. If you subtract cathode voltage drop of 33.3v from your plate voltage you get 363 volts. Multiply that by your cathode current, and you actually get 8.96 watts. Am I wrong?
i am a know nothing when it comes to electronics so pardon my ignorance if I am wrong but I was always told use the one hand rule on a live chassis or even a recently unplugged one, am I wrong? I just noticed you were handling it with both hands live BTW love the channel It has inspired me to crack open my dad's old 1960's era a beginning electrical circuits book, time to learn
Hi Ben, it's a good rule of thumb to follow, but rules are made to be broken. If I followed this rule to the letter each and every time I worked on an amp, I'd get nothing done. Some things you simply MUST be able to use both hands, soldering being one of those things, Installing or uninstalling components being another. Thanks for the comment and question! It's a good question. What I would suggest is getting yourself a good multi-meter and draining electrolytic caps every time you shut the amp down, then you can check for any remaining voltage in the caps if you're concerned about it. At that point, you can work freely inside the amp with both hands.
An old TV repair guy told me about working with one hand around high voltages. The idea is that were you to touch a high voltage point the charge could not flow across your heart muscle to ground via your other arm and make you slightly dead. Some guitar amps can have very high HT (B+) line voltages, which you don't want discharging to ground via you.
Wouldn't you get an artificially high reading if you're using the cathode resistor to measure the bias of your output tube because the cathode current is the sum of screen current and plate current?
+sa230e You can do the other method too of using the output transformer and you'll get a similar value. I think I misspoke in the video and said "cathode current" rather than "plate current". This video does a good job outlining the biasing method I used here: th-cam.com/video/L3rRk3eSTnA/w-d-xo.html
very informitive,my next project,if i can ever figure out what the amp "tec: did to myy 77 twin,besides blow n charge me for all tubes, though none of thr pres were replaced. thanks man,
If your amp blew when it was running under normal conditions & it wasn't a bad tube, the next thing would most likely be a filter capacitor. Worse, if the speakers in use were a poor match for the amp's output impedance (below 4 Ohms or above 16 Ohms speaker impedance), it might now have a bad power transformer. Find a shop with a good reputation and they'll make your amp better than new & won't rip you off.
Hey, I've got a '69 Vibro Champ, light comes on but no sound. Speaker responds to a nine volt so not blown. Tubes light up as well. Silly question but is there any correlation between a working light and a transformer not being blown to hell? Never had any smells, smoke, she just stopped talking one day but still lights up? Real sad thing, breaks my damn heart....Anyone have any ideas?
around 13:30 he determined that the main problem was a bad output tube. The process our host went through, and shared, is called trouble shooting. A 15 minute video and you couldn't watch it all the way through?
Most vintage tubes can handle the current voltages, and definitely modern replacement tubes are within spec now. I still think the volatages are slightly high, which I attribute to a manufacturing fault in the PT.
For me it is the opposite of that. I think he is a great amp tech, and I love watching his videos because it is just interesting to see the engineering and debugging process, and just the whole thought process of what one might go through in repairing an amp. I absolutely love this channel at times. It's like a place to go and hang out.
I've been designing building and repairing tube and solid state audio equipment for many years. He is nowhere _close_ to being a bad tech. I wonder what kind of work you do? I somehow doubt you have any examples to show us, though.
![CAMPปลิ้น | EP.83[1/2] เปิดแคมป์หลอนต้อนรับ 2 ตัวพ่อแห่งวงการผี!](http://i.ytimg.com/vi/2uPuHYHgwiI/mqdefault.jpg)
Holy shit. I just remembered why I started watching this channel. Amp repair
I have a very clean BF Princeton that worked great for years. During a gig the PT completely burned up. Smoke, and a sickly burnt marsh-mellow smell filled the club. Later when I got it on the bench, I discovered it had a 30 amp car fuse!! I had never checked it all the years I've had it.
Happens all the time. That's the reason for a fuse.
Great trouble-shooting and repair. A solid amp is the result!!
I have a Laney lc15r valve amp and the power transformer gets so hot after around 40 minutes of use that i can only touch it for 2 to 3 seconds only. What might cause this to happen ? regards. .love your videos.
To Christopher: "A bad amp repairman???" In my country they don't even exist anymore. So for me this guy is great. At least he's trying and has very good results. Today you just buy new and that's it??? He's not dead after repairing all that HV stuff so i think he knows what he's doing. Yeah he could be more safe but so do so many thrill seakers doing all that stupid stuff like bungee jumps and sorts. Everybody's got their own style of doing stuff. Don't buy all yhe stuff they teach you in school.
A current limiter would be a good thing to have in place while doing repairs on any amp. Just Saying, Keep up the good work!
When I was a kid (60s), if something didn't work, it was - take the tubes to the big tester at the drug store. So I thought that tubes failed, nothing inside. I didn't know what capacitors were for. Funny thing was, it often was the case, replace the bad tube, and it worked. Never was concerned that something caused a tube to fail. But I still check tubes first, usually indicates the problem area. Don
I think you erred when figuring dissipation. Aren't you supposed to subtract cathode voltage drop from plate voltage when figuring plate dissipation? You used cathode current times plate voltage for your calculations which gave you 9.77 watts. If you subtract cathode voltage drop of 33.3v from your plate voltage you get 363 volts. Multiply that by your cathode current, and you actually get 8.96 watts. Am I wrong?
i am a know nothing when it comes to electronics so pardon my ignorance if I am wrong but I was always told use the one hand rule on a live chassis or even a recently unplugged one, am I wrong? I just noticed you were handling it with both hands live BTW love the channel It has inspired me to crack open my dad's old 1960's era a beginning electrical circuits book, time to learn
Hi Ben, it's a good rule of thumb to follow, but rules are made to be broken. If I followed this rule to the letter each and every time I worked on an amp, I'd get nothing done. Some things you simply MUST be able to use both hands, soldering being one of those things, Installing or uninstalling components being another. Thanks for the comment and question! It's a good question. What I would suggest is getting yourself a good multi-meter and draining electrolytic caps every time you shut the amp down, then you can check for any remaining voltage in the caps if you're concerned about it. At that point, you can work freely inside the amp with both hands.
An old TV repair guy told me about working with one hand around high voltages.
The idea is that were you to touch a high voltage point the charge could not flow across your heart muscle to ground via your other arm and make you slightly dead.
Some guitar amps can have very high HT (B+) line voltages, which you don't want discharging to ground via you.
My amp stopped working. It now turns on but no sound and noticed a magnet that stuck to the power transformer. Is this bad? Could it be a fuse?
I wish you were local. I have a amp acting up and nobody around here works on them
Tucan Sam! I love it!
Wouldn't you get an artificially high reading if you're using the cathode resistor to measure the bias of your output tube because the cathode current is the sum of screen current and plate current?
+sa230e You can do the other method too of using the output transformer and you'll get a similar value. I think I misspoke in the video and said "cathode current" rather than "plate current". This video does a good job outlining the biasing method I used here:
th-cam.com/video/L3rRk3eSTnA/w-d-xo.html
very informitive,my next project,if i can ever figure out what the amp "tec: did to myy 77 twin,besides blow n charge me for all tubes, though none of thr pres were replaced. thanks man,
If your amp blew when it was running under normal conditions & it wasn't a bad tube, the next thing would most likely be a filter capacitor. Worse, if the speakers in use were a poor match for the amp's output impedance (below 4 Ohms or above 16 Ohms speaker impedance), it might now have a bad power transformer. Find a shop with a good reputation and they'll make your amp better than new & won't rip you off.
Hey, I've got a '69 Vibro Champ, light comes on but no sound. Speaker responds to a nine volt so not blown. Tubes light up as well. Silly question but is there any correlation between a working light and a transformer not being blown to hell? Never had any smells, smoke, she just stopped talking one day but still lights up? Real sad thing, breaks my damn heart....Anyone have any ideas?
Check continuity on your output transformer.
@@TheGuitologist : Thanks much!
what multimeter do you use?
So is the dude ever going to get to what the problem is/was? Damn dude you bounced around so much I forgot WTF was happening
around 13:30 he determined that the main problem was a bad output tube.
The process our host went through, and shared, is called trouble shooting.
A 15 minute video and you couldn't watch it all the way through?
its a 66 black,vibra. but ,first things first.
You think? You should know!
. Well, this makes sense. Resdesigning the power rail to supply proper plate voltages and thus plate currents is in order.
Most vintage tubes can handle the current voltages, and definitely modern replacement tubes are within spec now. I still think the volatages are slightly high, which I attribute to a manufacturing fault in the PT.
Short in primary maybe? I don't think someone would do a mistake on the winder..
Another bad phase inverter tube
I cant get past the thumb nail. Nasty.
If you want to repair tube amps dont do what this guy does. He's a great guitar player but sucks at repairing amps.
+Christopher Gillison I suck so bad the amp is repaired.
Suckiness stack overflow, gone so bad it went all the way around to fucking god.
For me it is the opposite of that. I think he is a great amp tech, and I love watching his videos because it is just interesting to see the engineering and debugging process, and just the whole thought process of what one might go through in repairing an amp. I absolutely love this channel at times. It's like a place to go and hang out.
I've been designing building and repairing tube and solid state audio equipment for many years. He is nowhere _close_ to being a bad tech. I wonder what kind of work you do? I somehow doubt you have any examples to show us, though.
It's called real world trouble shooting.
Our host shared his process, found the culprit (bad tube), and got the amp working again.