BG500 Tremolo opto

telstarventure
Regular Member
Posts: 24
Joined: Wed Dec 14, 2016 10:11 am
Contact:

BG500 Tremolo opto

Postby telstarventure » Tue May 30, 2017 1:30 pm

Have a technical question about the tremolo opto on my BG500 amp. Have been thinking that opto in my BG500 mite be bad looking at it looks like it has been replace before. Are they all the same or do they have different values? The problem having right now is when you switch the tremolo on there is a big volume drop. Any ideas?

Mr. Bill
Top Producer
Posts: 678
Joined: Tue Aug 19, 2008 12:15 pm
Location: Chicago, IL
Contact:

Re: BG500 Tremolo opto

Postby Mr. Bill » Mon Jun 12, 2017 10:06 am

No, optoisolators are not all alike.

Without knowing exactly how the circuit is designed, I can only offer up some possible causes for your problem.

If the voltage of the lamp is wrong, then the bulb may be turning on too soon causing the photoresistor to constantly shunt some signal to ground, causing the loss of volume.

If the resistance value of the photoresistor is too low, then whenever it is switched into the circuit it could be loading the signal down.

Are there any markings on the one that is currently in the amp?

telstarventure
Regular Member
Posts: 24
Joined: Wed Dec 14, 2016 10:11 am
Contact:

Re: BG500 Tremolo opto

Postby telstarventure » Thu Jun 22, 2017 5:12 am

The problem right now with the BG500 amp is when you turn off the tremolo with the footswitch the signal drops some. If you are using vibrato turning off at the footswitch it is fine. It only affects the tremolo. There is a adjustment trimmer pot, when adjusting the pot so that the signal doesn't drop at all but then the vibrato doesn't work. Also it have a double opto.

Mr. Bill
Top Producer
Posts: 678
Joined: Tue Aug 19, 2008 12:15 pm
Location: Chicago, IL
Contact:

Re: BG500 Tremolo opto

Postby Mr. Bill » Sat Jun 24, 2017 9:32 am

Again, without the schematic or the amp in front of me I'm only guessing here. It sounds like the variable resistor changes how bright the bulb in the opto gets, so if you adjust for the trem, the vibrato isn't strong enough. If you adjust for the best vibrato effect, the trem will cut some signal when shut off.

Does the amp have a single depth control or are there separate ones for the trem and the vibrato?


Return to “Amp Tech Q&A and Repair Shop”

Who is online

Users browsing this forum: No registered users and 3 guests