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Old 4th Sep 2022, 5:10 pm   #61
ColinTheAmpMan1
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Default Re: Fender Vibro Champ Amp

Fender were certainly known for putting rather high voltages on their output valves (I don't do US English, so I call them "Valves"). If you can use the original Fender valves, then they are likely to live through it. I don't know who fashioned the original Fender-labelled valves, but I would guess at General Radio - it will not be Fender, as I don't think that they made valves, just re-labelled them. From what I have read in various places, if you want to use newer valves and for them to last similar to the Fender-labelled ones, you should use Electro-harmonix ones. At least, that is what the suggestion is. If you look at a modern 6V6GT (also called 6V6EH - I think the EH is for Electro-harmonix) you will notice the "Made in Russia" addition to the label. I bought mine ages ago and I assume that they were probably made at the Reflektor establishment. If you don't want to help Mr. Putin at the moment, you may be able to get older ones.

Good Luck, Colin.
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Old 4th Sep 2022, 5:39 pm   #62
Bufo Bill
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Default Re: Fender Vibro Champ Amp

Thanks for the advice Colin. I am somewhat of a stickler for anglophone pronunciation and lingo but you get so many American responders when talking about fender amps I often drop the odd clanger and end up on the receiving end of "light-hearted banter" from both sides of the pond sooner or later!
If you'll forgive going off topic your Avatar picture shows a lovely mog and a lovely piece of kit I don't recognise. The make and model of tech and mog would be a lovely story to hear.
Cheers from Bill.
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Old 4th Sep 2022, 6:27 pm   #63
Kyri
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Default Re: Fender Vibro Champ Amp

Bill, and Colin, you may appreciate this picture. It was taken about 30 years ago, so moggy is long gone. I promise that I will make sure to be completely on topic in my next post, should this be out of place!

I still need to dig out my old champ and see what 6V6 it has, I suspect the original, but I am sure I got some spares (sylvania or RCA) years ago, "just in case" and never needed them.
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Old 4th Sep 2022, 7:01 pm   #64
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Default Re: Fender Vibro Champ Amp

Kyri, I love that picture right down to the Magic Roundabout wallpaper. That's one cool Kitty.
Now to Amplifier business! This amp was stored somewhere damp. A shed or a loft have to be top contenders, and my theory is that this has been the main cause of such a high rate of component failure.
Does this theory stand up to the experience of members who have dealt with similarly mistreated tech?

I have never come across a failing valve before. I know the valves are usually last in line to be chief suspects but I have checked all other component values both in and out of circuit. It's either a valve issue or a transformer problem. The mains transformer seems to get very only very slightly warm after a long period of activity and output voltages seem spot on when compared to the AB version of the schematic.
I have ordered a spare 6v6 to try a simple substitute test.
I will try that, but in the meantime would it be worth testing the little output transformer? Any suggestions for tests other than voltages?
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Old 5th Sep 2022, 9:58 am   #65
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Default Re: Fender Vibro Champ Amp

Hello,

Storing any electronic equipment in a damp environment is not desirable, and if it was over a long period the damp ingress will cause failures.

There were a brief discussion regards dampness in Fender amplifiers in this thread... https://www.vintage-radio.net/forum/...d.php?t=189878

I’ve had valves fail with short or open circuit electrodes. A valve in combo amplifier is subject to vibration which will eventually rattle the valve so much it could start to cause short or open circuit electrodes.

I was going through the toy box last week, and I have some old school 70’s(?) GE 6L6GC and 5881 pulls which may have some life in them – I’d have to find out.

Regards testing output transformers you can do basic resistance tests of the windings along with open and short circuits in the windings and shorts to the core etc. using a DVM or similar, however, to check the insulation of the windings you’d need an insulation tester. To check turns ratio, you’ll need a signal generator and an accurate AC meter… But saying all that, checking with a DVM, or similar meter will give a go no-go test on a transformer.

… I really should get that Mk4 Mullard valve tester I got I the Wotton Bassett auction in July commissioned.

Terry
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Old 5th Sep 2022, 2:35 pm   #66
Bufo Bill
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Default Re: Fender Vibro Champ Amp

Hi all, thanks for sticking with me. The new 6V6 arrived today, and now all voltages on the valves measure correctly and all functions work properly. Phew!

Now to give it a jolly good thrashing!
Cheers from Bill.
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Old 5th Sep 2022, 6:16 pm   #67
ColinTheAmpMan1
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Default Re: Fender Vibro Champ Amp

For the benefit of Bufo Bill (and possibly others wondering), the 'scope is a Tektronix 7623A, of which my good friend John Sykes was sorting out the HV circuitry. I still need to go and pick it up. It also has storage, which I managed to mess up. Unfortunately, John's expertise meant that it still doesn't do storage properly. If anyone can point me in exactly the right direction to sort this, I would be delighted (this was the bit to ensure that this posting is still on-topic).

The cat is a female called Tallulah, but she is regrettably poorly at the moment. She isn't using her legs quite as well as could be hoped, but plenty of food and the medication from the vet seems to make her a little better.

I am aware that the subject of my well-being was discussed some while ago. I am still not quite right (my wife has dementia and is in a care-home, I had bladder-cancer and there's the cat's health, too) but I am improving bit-by-bit. I send my thanks to you all for being such good friends.

Colin.
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Old 5th Sep 2022, 7:27 pm   #68
stevehertz
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Default Re: Fender Vibro Champ Amp

Fight on Colin, life is for living but sometimes it's not just a matter of going with the flow, we have to face - and fight - adversity. I had cancer 18 months ago (operable and now sorted) and was hospitalised a couple of months ago with AKI (acute kidney injury (infection)) and am still recovering, and next week I've got a cystoscopy to look forwards to (again). It's an age thing I guess, but otherwise I regularly ride my mountain bike at neck breaking speeds, a strange juxtaposition I know. Best of luck to you.
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Old 8th Sep 2022, 5:03 pm   #69
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Default Re: Fender Vibro Champ Amp

There is nothing adequate I can say to show my admiration for the fighting spirit of the two of you. I have thought about you both for several days now, racking my brain trying to think of something to encourage or console the two of you. But you don't need that, you both have a strength that I can only wonder at.
The help everyone has given with this amp is much appreciated and it is working beautifully. I'm really pleased.
I think this would be a good place to close this thread, if one of the Moderators would oblige.
Many thanks from Bill.
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Old 8th Sep 2022, 5:18 pm   #70
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Default Re: Fender Vibro Champ Amp

Thanks for those kind words Bill.
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Old 9th Sep 2022, 2:02 pm   #71
ColinTheAmpMan1
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Default Re: Fender Vibro Champ Amp

Bill,

On my part, there is no need to "admire" my fighting spirit. All of these things happened naturally and I didn't have a choice. It was either get on with life or what? Having said that, I thank you for the kind words, too.

Good Luck and may you enjoy the Fender Vibro Champ.

Colin.
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Old 9th Sep 2022, 3:48 pm   #72
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Default Re: Fender Vibro Champ Amp

As Bill has said, the thread has done its job, and plenty of appreciation has been expressed, so it's a good place to close. I'll do honours.

David
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