How to repair Fender Champ tube guitar amp Intermittent audio D-lab
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- Опубліковано 9 лип 2024
- This amp showed up at D-lab electronics in need of repair. Sound level dropping out. I thought, why do my typical, fix using an oscilloscope, why not an old VTVM? Well, here it is .. in the old days, the VTVM meter was the cats ass. D-lab still troubleshoots the old fashion way. This is my legacy to you, my god friends.
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I have been watching Terry for a long while. Yes the VTVM, oscilloscope, are very useful. But the man behind them is more important. Thank you very much Terry for being a very good teacher.
Preaching to the choir here....
Those warping old Fender circuit boards are great for repairs caused by the boards itself.
You can see the warping in the area of the cap failure.
Excellent video about old analog meters. Definitely easier and safer than setting up a big oscilloscope, variable iso transformer, audio generator, etc.....
Heck of a lot cheaper!
Thank you for the video!
You have old school vacuum tube theory for sure that's priceless. thanks
I like your impresario, "Mr. Dual Triode Guy"! He's a class act.
Your whole point here is of great value! I wouldn't be without my VTVM's in the shop. Great for peaking IF stages on an old AA5 as well as being able to take voltage measurements without loading down the circuit under test since tubes are hiZ devices, and the VTVM is the perfect marriage. DVM's, like digital oscilloscopes, are constantly refreshing and can drive you to drink...(not a bad idea during a rough day) :) CRT scopes will always reside at my shop :). One of my favorite VTVM's is the RCA WV98C which I lost on a service call...it grew legs. Wish I could locate another one...even if I have to restore it. This was a great tip for the newbies, and a reminder for us veterans :) Keep 'em coming...I'm a watchin' :)
Hey Mr. D-lab, good on you for acquiring a VTVM! There is another way in which these beasties can be used, look at the very bottom scale - the little minus-zero-plus bit. To use this, use the zero control to make the meter read the centre of this scale & it will show not only positive readings but negative readings also. Comes in very handy when aligning IF transformers. Also these meters have an input impedance comparable to that of a digital meter. Thank you for another bloody good video. I salute you good sir.
Did you call it? Terry, you ALWAYS call it! Your knowledge of vacuum tube/valve circuitry, component behavior and aging never fails to astonish me! Again, NAILED IT!
Thank you my friend :)
Hi Terry, watching your videos regularly - everything looks simple and easy - thanks for sharing your unconventional way of fixing amps.
Thanks for all you do, lot's of effort on your part Mr. D.
Excellent! Still catching up on the d-lab videos. Yes, for certain applications you can’t beat a VTVM!
Nice repair Terry and I figured that you would find it pretty quick.
I collect old VTVM's. I've got Eico's (259 on the bench right now), a giant old Hickok Model 209, a couple of RCA Voltohmyst's and one Senior Voltohmyst, and my never been used Simpson Model 303. You can't beat the old analog vacuum tube meters.
73
NE5U
Hello, I had quite the collection of these meters at one time. Decided to keep the Heathkit and send the others down the way. B&K made one that had a dampened needle. I'd stay away from that type. In this application, you want quick needle response. Thanks for your kind responses to my presentations. TD
Nice. I got two of those Heathkit VTVMs last ham swap meet for $5 each; I didn't really need them, but they had been repaired and I really couldn't resist. Gotta make probes; those are not quite so trivial with that special TRS phone plug with the insulating bushing in the middle. Otherwise, any old phone plug will work as long as you lay off measuring big volts. I may just hard-wire in some leads.
Foi bem explicado em seu vídeo. Os medidores analógicos ainda são parte fundamental em toda bancada de reparação e montagem de eletrônicos. Excelente vídeo...!!!!
Very nice work indeed ,yes very good d-lab keep up the great work .I can't wait to see what assignment you get next.
Cool deal.. I have a few analog budget meters around. It would work for this sort of thing. The school always said it had to be Simpson or Triplett, or it was a joke... I don't believe them. I started with some "poor man" meters, and they earned their keep til I could upgrade.
There are analog multimeters still available to buy in our equivalents to dollar stores here in Brazil. haven't checked prices recently, but last time I saw 'em, they went for something between 1 and 2 bucks.
"Hit it on the top". Known as percussive maintenance.
I already have an Eico 221 and recently acquired an RCA Master Voltohmyst WV-87A and a Master Voltohmyst WV-510A.....Nice :-)
The VTVM's are a great addition to any test bench. I especially like the Heathkits. Sure wish those kit days did not end. When I was a kid, I'd spend hours with the new Heathkit catalog. TD
This is a great tip about the VTVM Terry. I happen to have an old Heathkit one and will have to give this method a try. Gotta say though, that IP-32 in the background is a beauty! Still got that?
Outstanding!
Thanks!
Reading the comments, I found the VTVM 5 vac setting reply. What signal generator settings did you use? And, if I may, I have always wondered: why can't one use an 8 ohm speaker core as a dummy load? So much obliged for the great tutorials
I've got an old analog meter I bought new from radio shack years ago that has been accurate on all its settings. It's been a really good meter. But a VTM would be nice to have too.
Very Good!!
hello and I've got to say I love your videos and all the great information you put out there for everyone so that being said I have a question about capacitors , I am in the process of ordering a assortment of capacitors so my question is how critical is the voltage. I noticed a lot of the assortment of capacitor kit range around 50 volts so that being said I would think that if I'm going to be working on tube amps and Tube radios I would need at least a voltage of 2 - 300 volts to put me in the good range is this true? Any information you can give me on this would be much appreciated thanks and keep up the good work.
Nice vid!
What type of glue do you use? Looks like duco. Would silicone be strong enough to hold it? I wouldn’t want anything that would be hard to remove later.
Hi Terry,
I really enjoy your videos and the knowledge your share.
Out of curiosity, what model Heathkit VTVM do you use?
Thanks, Lee
Thanks man, My VTVM is the IM-5218, a very nice unit. Love Heathkits
D-lab Electronics thanks!
thanks for your video very helpful !
i have a question about the 8 ohms dummy load resistor
should we only use a non inductive resistor, instead of a regular one ? is it risky to do so ?
or it is just for precision ? i tried with a regular one and it works just fine. thanks you.
Hello, Yes, it really doesn't matter. If you can find the non inductive type, that would be the first choice
thanks a lot for your answer
You called it fur shur. And without a glass of vino beforehand. Lol
Had the vino afterwards. Great repair issue with quick resolve. Thanks for your faith in me. TD
Very nice job, what do you set it on like AC 10 volt range..
Thank you Sir, Yes, the meter was on AC volts. This one has a 5 volt range.
D-lab Electronics
Thanks.
Question: would a 100 ohm resistor be too small to discharge the filter caps capable of holding up to 500V?
I would suggest at a 1K resistor. The cap voltage discharges quickly, however with a 100 ohm resistor, you may get a spark
Awesome thanks!
Terry,,, gotta say that it is really hard to watch with the audio out of sync that much. Great vid if not for that friend.
Carl
Hello Carl, Just watched the vid here, no sync issues, No other comments regarding this problem. Could be a UA-cam or server issue in your area? Sorry for the problem. TD
Not sure what the heck happened. I just went in and looked again and now the audio is right on. That was kind of freaky weird.,,,, Anyway,,, great fix on the amp,,, love those Champs.
Carl
tweak that amp wit da v t v m boy! oh yaaaaah
D labs da shit
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