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Topic: 400 Limited effects jacks problem |
Dennis Detweiler
From:
Solon, Iowa, US
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Posted 26 Aug 2021 7:19 pm |
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Session 400 Limited effects send/return patches on front panel cause feedback when I connect a delay or reverb pedal to either one of the loops. If I turn off the post and pre gain it still creates a loud feedback as soon as I power the amp up. Both pairs of the send/returns have the same results. Is there a faulty IC in this circuit? The jacks and contacts have been cleaned.
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1976 Birdseye U-12 MSA with Telonics 427 pickup, 1975 Birdseye U-12 MSA with Telonics X-12 pickup, Revelation preamp, Carbon Copy Delay and Hall Of Fame Reverb, Crown XLS 1002, 2- 15" Eminence Wheelhouse speakers, ShoBud Pedal, Effects Pedals. 1949 Epiphone D-8. |
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Steven Paris
From:
Los Angeles
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Posted 26 Aug 2021 7:34 pm
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Are you sure you're not connecting it backwards? Try reversing the in and out cables.
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Emmons & Peavey |
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Dennis Detweiler
From:
Solon, Iowa, US
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Posted 26 Aug 2021 7:59 pm
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I have the manual for it with pictures of how to connect the pedals. Amp send jack to effect pedal in. Effect pedal out to amp return jack.
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1976 Birdseye U-12 MSA with Telonics 427 pickup, 1975 Birdseye U-12 MSA with Telonics X-12 pickup, Revelation preamp, Carbon Copy Delay and Hall Of Fame Reverb, Crown XLS 1002, 2- 15" Eminence Wheelhouse speakers, ShoBud Pedal, Effects Pedals. 1949 Epiphone D-8. |
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Steven Paris
From:
Los Angeles
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Posted 27 Aug 2021 12:25 am
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Try just a cable from send to return on the amp. If that works fine, that will tell you that the problem is most likely NOT the amp.
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Emmons & Peavey |
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Dennis Detweiler
From:
Solon, Iowa, US
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Posted 1 Sep 2021 5:25 am
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Evidently you can't chain two or more pedals together and patch into one of the send and return patches. If I use each of the two send and return with a single pedal in each it works fine. The amp circuitry was probably built for a delay in the first patch and reverb in the second (common setup)between the pre-amp and power amp stages.
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1976 Birdseye U-12 MSA with Telonics 427 pickup, 1975 Birdseye U-12 MSA with Telonics X-12 pickup, Revelation preamp, Carbon Copy Delay and Hall Of Fame Reverb, Crown XLS 1002, 2- 15" Eminence Wheelhouse speakers, ShoBud Pedal, Effects Pedals. 1949 Epiphone D-8. |
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Larry Dering
From:
Missouri, USA
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Posted 1 Sep 2021 3:10 pm
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| Dennis, I wasn't aware of that so now I have to try it out on my Session 400. Seems odd. I have patched a Peavey Profex II through the loop with no issues. |
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Dennis Detweiler
From:
Solon, Iowa, US
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Posted 2 Sep 2021 5:55 am
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I've been using the first patch for my pot pedal which I think was its intended use. The two patches between the pre-amp and power amp has been my issue. I haven't tried the patch on the rear of the amp.
I'm also having issues with the reverb circuit. When I bought the chassis there was no tank with it. I bought a new tank for it (NOS original), but it produces a lot of hum. I tried reversing the input and output on the tank, but still getting hum. If I turn it off or unhook the pan it is quiet. I found another post on the forum and will replace the 4558 chip in the reverb circuit and see if that corrects the problem. I use a reverb pedal anyway, but would like the amp factory functional.
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1976 Birdseye U-12 MSA with Telonics 427 pickup, 1975 Birdseye U-12 MSA with Telonics X-12 pickup, Revelation preamp, Carbon Copy Delay and Hall Of Fame Reverb, Crown XLS 1002, 2- 15" Eminence Wheelhouse speakers, ShoBud Pedal, Effects Pedals. 1949 Epiphone D-8. |
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Larry Dering
From:
Missouri, USA
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Posted 2 Sep 2021 1:15 pm
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| I believe the Ken Fox harness solved many of these hum problems. Should be a few discussions on this from the forum. |
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Dennis Detweiler
From:
Solon, Iowa, US
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Posted 2 Sep 2021 3:11 pm
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I have an upgrade kit in the amp. Can't remember who wrote it up. I bought the Burr Brown chips and caps through Mouser and switched the parts out several years ago. One post by Ken suggested the reverb chip was faulty. I replaced the Burr Brown chip with an original 4558 and the hum is gone. However, the reverb signal is weak. It has to be nearly full on to get adequate reverb. Another part probably needs replaced to bring the signal up? I'll post the problem in a separate post and see if someone can remedy.
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1976 Birdseye U-12 MSA with Telonics 427 pickup, 1975 Birdseye U-12 MSA with Telonics X-12 pickup, Revelation preamp, Carbon Copy Delay and Hall Of Fame Reverb, Crown XLS 1002, 2- 15" Eminence Wheelhouse speakers, ShoBud Pedal, Effects Pedals. 1949 Epiphone D-8. |
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