Reverb Hiss Kustom Lead I [message #16309] |
Sat, 22 October 2011 06:08 |
blindmouse
Messages: 25 Registered: February 2011 Location: The Netherlands
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Junior Member |
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I fixed and restored my recently purchased Kustom Lead I. The only thing I still need to do is replacing the big filter caps. (I did put in some new F&T's but one was open and blew two rectifiers) There still is a small issue: turning up the reverb from zero an increasing amount of hum is added to the signal. I cleaned all reverb connectors. Now the MC1458 dual opamp provides the reverb signal. Could it be this opamp that causes the hiss?
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Re: Reverb Hiss Kustom Lead I [message #16313 is a reply to message #16312] |
Sat, 22 October 2011 12:10 |
blindmouse
Messages: 25 Registered: February 2011 Location: The Netherlands
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Junior Member |
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I'm so sorry. I wrote the word 'hum', I meant the word 'hiss'. There is no hum on the reverb. There is a hiss that troubles me.
Some updating:
- There is also that so called 'frying eggs popping' sound;
- The hiss and frying eggs sound stay when drive and volume are down to zero.
[Updated on: Sat, 22 October 2011 14:04] Report message to a moderator
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Re: Reverb Hiss Kustom Lead I [message #16321 is a reply to message #16314] |
Sun, 23 October 2011 10:37 |
blindmouse
Messages: 25 Registered: February 2011 Location: The Netherlands
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Junior Member |
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Well, some work to do.
I just ordered some 2200uF/63V Vishay filter caps, some 3A 1000V rectifier diodes and some 4558 dual op amps. When they come in I'll start working on the amp again. Played it through a reissue Jensen C12R. I really did like that sound.
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Re: Reverb Hiss Kustom Lead I [message #16339 is a reply to message #16321] |
Sat, 29 October 2011 06:33 |
blindmouse
Messages: 25 Registered: February 2011 Location: The Netherlands
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Junior Member |
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I got the stuff in and first started to replace the 1900uF/40V filtercaps with the new 2200uF/63V ones. Fired it up with a '100W lightbulb in series' and it all looked good. Then gave it the 230V and played the amp. Sound was good, a bit more bassy, but I adjusted that with the bass-knob. The I tried to put in the 3A 1000V rectifier diodes. The leads were too thick and I replaced the two original ones I hadn't replaced before with 1A 1000V ones. Now I noticed these four rectifiers came in two pairs: the blown ones are 500V and the ones that did not blow are 300V ones! The rectifiers done I fired up the amp and everything was ok. Now I put in a new dual op-amp for the reverb/tremolo circuit. The original one, a 1458 I replaced with an upgrade, a 4558, I also installed an op-amp adapter. When I fired the amp up I noticed a difference in sound. It sounded cooler, flat, the emotion had gone. I put back the original 1458 and that good old familiar sound was back again. Are my ears fooling me???
Changing out the op-amp didn't take away the 'frying eggs' sounds. Cleaning the reverb pot didn't either. When I disconnect the reverb pan completey (both input and output) the unwanted sound is still there. Any ideas????
Thanks and kind regards.
[Updated on: Sat, 29 October 2011 06:48] Report message to a moderator
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Re: Reverb Hiss Kustom Lead I [message #16346 is a reply to message #16341] |
Sat, 29 October 2011 14:48 |
blindmouse
Messages: 25 Registered: February 2011 Location: The Netherlands
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Junior Member |
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No hiss, no 'frying eggs' sound with the pre amp board disconnected! So it is the pre amp board I guess. Could it be the 80848 IC (I3 on the PC5129 board) that's causing trouble?
Does solid state amps have 'plate resistors' like tube amps? Bad tube amp plate resistors can cause the weird frying eggs sounds.
Thanks
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Re: Reverb Hiss Kustom Lead I [message #16347 is a reply to message #16309] |
Sat, 29 October 2011 21:27 |
chicagobill
Messages: 2005 Registered: April 2003
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Senior Member |
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Yes, the other chip can also be the cause of the noise. These solid state amps do not have plate resistors, but some of the resistors have a similar function and can also contribute to the noise.
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