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Old 12-01-2012, 03:15 PM   #1
pjutter
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Join Date: Dec 2012
Engl E530 problem. Help!

Hi

I have a problem with my Engl E-530. When engaging the switches the amp switches channels like it should. However the Led's of the "hi/lo gain" switch and "clean/gain" switch are not working. The Led's light up very very shortly after engaging the switches, but that's it. So the Leds themselves are not broken, it seems to be a problem in the circuitry. When measuring with a multimeter across the Led's when engaging the channels, shortly I measure 2,1 volts, but then the voltage drops and also the Leds are off. It concerns Led HL3 and HL4 on the schematic.

The Leds of the "contour" and "preamp defeat" switch work correctly (HL2 and HL1).

After visual inspection of the circuitry I found out that transistor J175 (VT1) was broken. So I replaced it with a new one. But this didn't solve my Led problem. Actually I didn't notice any difference at all.

Can someone tell me what to look for? Where does the power for the HL3 and HL4 Leds come from?

Here's the schematic of the amp:

http://music-electronics-forum.com/...riginalplan.jpg
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Old 12-02-2012, 05:35 AM   #2
pjutter
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Anyone?
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Old 12-02-2012, 06:15 AM   #3
R45VT
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Free bump. When I get back to my computer tomorrow I can take a peek at the schem.

What type of diagnostic equipment do you have?
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Old 12-02-2012, 06:30 AM   #4
pjutter
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Ok thanks. I only have a multimeter.

Some more information:

I have checked the connection of the leds, they seem fine. Strange thing is of course when you engage the switches that the led's light up very shortly, then the voltage drops. Is there some component in the signal path of the leds that should keep the voltage to the leds constant, but might be broken?

The relays work ok, changing channels works ok.

When I connect a footswitch to the jack, then the leds on the footswitch work but still not on the amp. I just cleaned the footswitch jack and it does not make a difference. So I assume it's not a jack problem. Again, the Leds on the amp light up shortly when using the footswitch.
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Old 12-02-2012, 07:11 PM   #5
R45VT
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Link is broken.

Also its great you took your measurement across the LED but now take a measurement from ground to either side of the LED and update with the results.
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See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.

Last edited by R45VT : 12-02-2012 at 07:41 PM.
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Old 12-03-2012, 06:20 AM   #6
pjutter
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I found out the 2 leds are broken! I don't understand how they could light up shortly though. But I soldered 2 new ones in and it works now.
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Old 12-03-2012, 09:15 AM   #7
R45VT
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Good job!
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See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
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Old 12-03-2012, 04:04 PM   #8
tas38
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Two cheap amps in tampa area
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