| Reverb issue with 72/73 Kustom 250 head [message #26592] |
Fri, 02 March 2018 19:07  |
Ernieiv
Messages: 5
Registered: March 2018
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Junior Member |
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Wondering if anyone can give me some tips on fixing my reverb issue in my 250 head. When I bought the amp the reverb tank was not present. I bought a replacement from MOD, however it is not working. When I plug in or up plug the RCA wires from the tank to amp it gives a tank splash sound but nothing else. Is something going on with my reverb circuit-board? Any suggestions?
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| Re: Reverb issue with 72/73 Kustom 250 head [message #26595 is a reply to message #26592] |
Sat, 03 March 2018 06:30  |
stevem
Messages: 4774
Registered: June 2004
Location: NY
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Senior Member |
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what part number Mod tank did you order?
Hearing the tank crash means these 3 things.
1) the output side of the new tank is good.
2) the rca cable from tank to board is good.
3) the recovery amp on the effect board is good.
Trouble shooting.
Is this the same issue that prompted you to get the new tank?
If so then get a known good rca cable on the input side of the tank.
Confirm it's good by hooking it up to the output side of the tank and listen for the crash.
If this test proves out then report back and we will help you trouble shoot the input side issue you have .
It's also possible your new tank is defective in the same way your old tank is!
[Updated on: Sat, 03 March 2018 06:32] Report message to a moderator |
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| Re: Reverb issue with 72/73 Kustom 250 head [message #26596 is a reply to message #26595] |
Sat, 03 March 2018 15:48 |
Ernieiv
Messages: 5
Registered: March 2018
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Junior Member |
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Thanks so much for the suggestions!
So, I tried a know good rca cable but still same issue. When I bought the amp there was no tank, So, the MOD tank I bought is a P-RMOD-4FB3A1B, I bought this because it's supposed to work with many 70's Kustom, perhaps there is a different one? I just took my best guess, I know Kustom used a Few different tanks. I do know it's a 17" by the screw wholes. Also I was off on the date it's a '74. Any clues?
Thanks
[Updated on: Sat, 03 March 2018 15:49] Report message to a moderator |
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| Re: Reverb issue with 72/73 Kustom 250 head [message #26597 is a reply to message #26592] |
Sat, 03 March 2018 21:32 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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There is one problem with the tank that you picked, actually more than one but the most important one is the input grounding.
The input transducer is part of the feedback loop of the driver op amp, so the RCA input jack should not be grounded. Check the jack to see if you can just clip a jumper wire or something to isolate the ground connection of the input jack from the metal case.
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| Re: Reverb issue with 72/73 Kustom 250 head [message #26604 is a reply to message #26592] |
Tue, 06 March 2018 08:22 |
stevem
Messages: 4774
Registered: June 2004
Location: NY
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Senior Member |
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If you got a replacement pan for the plexy face amps ( k100 and 200s ) the input impeadence is not right for a metal face K150, 250, 300 or 600 , these reverb pans need input resistance as seen on a ohm meter of only 58 ohms, not the 180 ohms of the early Kustom pans.
In one of my 250s that has a replacement Accutronics pan it's got a 4FB3A1B pan and the amp has more reverb then you could ever use, and for some reason the input is not connected to the ground of the pan tank.
I can only guess that who ever put it in the amp before I got it lifted the ground on that input because it should not have been made that way!
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