Engl E530 problem. Help!

[pjutter]

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/a...iginalplan.jpg

[Enzo]

First thing I'd look at would be for dirty contacts in the footswitch jack.

Look for cracked solder on one or more of the LEDs. It sounds to me more like a bad connection somewhere than a bad part.

The current for HL3 comes through R101 and RE2 coil. The current through LH4 comes through R103 and the coil of RE4. If your channels change OK, then the relays must be working, and that directs us back to the LEDs themselves or the jack.

[pjutter]

Thanks for answering.

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?

Yes, the relays work ok, changing channels is 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.

[drewl]

Can you monitor the voltage going to the LED's?
Does it rise slowly until the LED's turn on, or does the voltage stay the same?

[pjutter]

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!
thanks for replying to this post!