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Post subject: Champ600 troubleshoot
Posted: Sun Mar 17, 2013 9:53 am
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Hi all
Someone living near me put a perfect looking condition champ 600 on the side of the road. It was minus a speaker. I have ordered and installed the Jensen speaker and a new tube set from amplified parts. Before replacing the tubes, I'm pretty sure the preamp tube was not illuminating and the power amp tube was illuminating.
I have spent some time on the trouble shooting amp site and Measuring ohms, and I believe that I may have a dead transformer.
The symptoms are: Power on-jewel light on. No sound...nothing. The preamp tube (12AX7) does not illuminate, the power tube 6V6 does illuminate.
I am hoping it is a component fault like the transformer that I can re and re vs a diode/resister.

Any advise or hint will be greatly appreciated.
Thx Rick


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Post subject: Re: Champ600 troubleshoot
Posted: Sun Mar 17, 2013 1:03 pm
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Schematic here ;

support.fender.com/schematics/guitar_amplifiers/Champion_600_schematic.pdf

IMO Transformer do not look bad with what you say .

1- Is the amp working before new speaker ? Or before some work you do ?

2- Do you hear hum from the speaker now ? Speaker is good ? Wring to the amp?

3- 12AX7 tube not glow , try a new one or take a voltage reading on heater ; pin 4 (or 5) and 9 = 6.3 AC volts. Amp power ON. Pins 4,5 are solder together

Or read ohms on tube ( tube remove fron the amp ) pin 4 and 5 = 8 ohms and 4 to 9 =4 ohms and 5 to 9 =4 ohms; this mean tube heater is good.

Be careful , tube amp have voltage that can kill you.
Can you read a schematic and take some other reading !


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Post subject: Re: Champ600 troubleshoot
Posted: Sun Mar 17, 2013 1:39 pm
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+1.

Sounds like a bad heater line to the 12AX7. Make the measurements stratele52 suggests.

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Post subject: Re: Champ600 troubleshoot
Posted: Sun Mar 17, 2013 4:36 pm
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Sounds like you should just put it back on the side of the road and let someone else deal with it. What did you say your address was? :wink:

In all seriousness, follow the advise given and you should be ok as long as you know how to read schematics.

Good luck.

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Post subject: Re: Champ600 troubleshoot
Posted: Mon Mar 18, 2013 9:09 am
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Thx very much for the replies. Speaker and tubes are brand new. I have done some testing of resistance of the primary windings and ( if I did it right ) I believe there is a short and the transformer is bad. I will test the preamp tube and study the schematics and report back...in about a week.
Cheers
Rick


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Post subject: Re: Champ600 troubleshoot
Posted: Mon Mar 18, 2013 9:24 am
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Transformer reading with ohmeter do not say anything unless you are a pro. Resistor are too low.

Voltage reading IS THE ONLY WAY to know unless fuse always blow.


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Post subject: Re: Champ600 troubleshoot
Posted: Mon Mar 18, 2013 9:42 am
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I agree with Stratele, transformers use AC to work. Not DC. Measuring static DC resistance is really only good to see if you have a break in the windings (infinite resistance).

An AC signal input (like a signal generator) and measuring AC voltages will give you the data needed to find AC impedance values. Then, you can compare these to a data sheet.

There are several books and even online sites to diagnose a bad amp. Best to follow some kind of stategy to rule-out the various sections of the amp.


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Post subject: Re: Champ600 troubleshoot
Posted: Mon Mar 18, 2013 12:39 pm
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Norskeman1 wrote:
The symptoms are: Power on-jewel light on. No sound...nothing. The preamp tube (12AX7) does not illuminate, the power tube 6V6 does illuminate.


This points to a heater problem for the 12AX7. Since the pilot light works and the 6V6 glows, check the green twisted heater wires that run between the 6V6 and 12AX7 and make sure the solder connections are good.

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