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 1 
 on: Today at 03:00:37 PM 
Started by solidstate2199 - Last post by tonyharker
I expect the electrolyte just dried out, which can happen after a few years.  The ESR goes high it gets hot then BANG!  Checking the ESR of a capacitor is a good test of its health.

 2 
 on: Today at 02:38:13 PM 
Started by solidstate2199 - Last post by Enzo
Probably not overvoltage.   PArts can fail, there is not always a direct cause you can determine.  There could have been a small defect in the part originally that just now finally gave way. 

 3 
 on: Today at 01:22:59 PM 
Started by KMG - Last post by rankot
I started low voltage fet experiments with Victor Kampf idea.
http://www.sugardas.lt/~igoramps/article68/article.htm
But sound was not close enough to tube one & I moved to high voltage experiments.

I tried to read Victor's article, but I am not sure what is Rc value on this page. Could you please explain it?

 4 
 on: Today at 01:03:42 PM 
Started by solidstate2199 - Last post by solidstate2199
Hi Folks.

i bought a 1988 Laney AOR which works fine. Nice Amp.

One thing which caught my interest is that one of the 6 filtercaps
has been changed sometime ago.

As i open all my new amps to check the overall condition i discovered that
this capacitor must have really blown wide open because there were lots of
residue in the headshell directly under that spot.

What causes this? All other 5 L.C.R. caps looking fine without any dimples on top due
to age.

Im curious to what causes such an event. I guess too much voltage? (caps are 50uf/50uf 500vdc)

Thanks for your insights.

 5 
 on: February 28, 2017, 10:01:01 PM 
Started by sonolink - Last post by Enzo
"Complaint" simply means problem specified.  it is not a description of mood or attitude or anything.  AMp makes enough noise to be unusable, that sounds like a valid complaint to me.


Even if the FX is turned down, the FX circuit is still in there running, and it is digital.  Digital hash can leak out into other sensitive circuits.  SO it COULD be the source of the noise without directly affecting the FX themselves.  or it could be totally innocent.

COntrols that affect the noise are after its source.  COntrols that have no effect are either before the source or not in line with it.  That can be tricky, if the digital circuit is noisung up the power supply, it might inject that noise into earlier circuits.

The main power supply is going to make hum, plain old 60Hz hum, if it has problems.  Unless it is an SMPS, it won't make that noise.

And missing ground connections internally can be possible causes.


 6 
 on: February 28, 2017, 08:04:38 PM 
Started by sonolink - Last post by J M Fahey
Hello

Thanks for your reply Enzo. It's not a "complaint". As you can hear on the linked recording the noise makes the amp unusable. I'm trying to repair it. It IS the amp. I've tried it in different places before posting.
Here everybody is suspect unless proven innocent, so pease run the tests suggested above and describe what happens, control by control.
*You*  have the amp, not us, so please do the tests we ask you, even if you find them useless.
And we ask *only*  what we would do ourselves if we had the amp on a service bench.
Suppose the amp does power up and you say: "its not the fuse, I put a new one there before leaving home"
Guess what well do?
Yup, you are right, we will check the fuse anyway .And so on.

Quote
The controls do affect the noise as you can hear on the linked recording. Gain, Volume, Bass, Middle, and Treble, and each position of the amp simulation knob. This happens on BOTH channels with the FX return knob down to zero.
How would we know that?
Its not a video so we have no clue whether you are touching any knob or not, nor you say "now Im sweeping treble from 0 to 10" or"now Im turning around" or "Im putting the guitar horizontal"  or whatever.
FWIW buzz drops *a lot* from 0:12 to about 0:22, yet guitar volume stays about the same, so you did NOT touch the volume control, so *what* did you do at that moment?
Theres also a noise burst at around 0:31 , plus other unexplained changes, but again, why should we solve a riddle?
Quote
SO, my guess is the noise is produced somewhere else than the FX circuit OR if it is produced by the effect circuit it reaches elsewhere somehow.
Why?
Quote
You may be right and maybe it's digital hash but, just out of curiosity, COULD it be a PSU noise? I'm not sure but I think this amp works with a bipolar PSU and I'm not very acquainted with these. Could it be a source of noise if some component is dead?
Hum, maybe; but this kind of noise, very unlikely.
Quote
Anyway I'll check the DSP card as you suggest :)
The DSP crd and all other tests suggested in the same answer.
Quote
Also, I can't find a damn schem of this amp. Any one?
I dont have it, but in similar amps I have seen that the main circuit is exactly the same, only instead of the spring reverb circuit you have a nice 6 or 8 pin flat cable connector labelled "To - From DSP card" or FX board , so main circuit can be btroubleshooted the normal way, and DSP card either works properly or not.
Absolute worst case, I guess you can unplug it and keep the effects less amp working.

 7 
 on: February 28, 2017, 06:58:35 PM 
Started by sonolink - Last post by sonolink
Hello

Thanks for your reply Enzo. It's not a "complaint". As you can hear on the linked recording the noise makes the amp unusable. I'm trying to repair it. It IS the amp. I've tried it in different places before posting.

The controls do affect the noise as you can hear on the linked recording. Gain, Volume, Bass, Middle, and Treble, and each position of the amp simulation knob. This happens on BOTH channels with the FX return knob down to zero.

SO, my guess is the noise is produced somewhere else than the FX circuit OR if it is produced by the effect circuit it reaches elsewhere somehow.

You may be right and maybe it's digital hash but, just out of curiosity, COULD it be a PSU noise? I'm not sure but I think this amp works with a bipolar PSU and I'm not very acquainted with these. Could it be a source of noise if some component is dead?

Anyway I'll check the DSP card as you suggest :)
Also, I can't find a damn schem of this amp. Any one?
Cheers

 8 
 on: February 28, 2017, 05:42:36 AM 
Started by sa230e - Last post by joecool85
Wow! That's a looker! Great job!

Sent from my XT1055 using Tapatalk


 9 
 on: February 27, 2017, 09:17:23 PM 
Started by sa230e - Last post by sa230e
Can we have some pics of this amp?  It may or may not help us help you, but it will definitely be interesting to see!   :tu:

Sure, here's a few pics I took when it was working. The matching speaker cabinet is also homemade. It has a single 12" Celestion Greenback in it.






I thought it turned out pretty nice for a first try. The inside, not so much. It's hard to do point-to-point wiring cleanly. Next time, I'm using turret board.



I designed the head to have a bottom plate so to work on it you just flip it upside down and take the plate off and you're in. You don't have to remove the chassis from the head.

 10 
 on: February 27, 2017, 07:05:12 PM 
Started by sa230e - Last post by joecool85
Can we have some pics of this amp?  It may or may not help us help you, but it will definitely be interesting to see!   :tu:

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