Gain problem with Amp

[bkkcheesepie]

Hi any amp tech can help me troubleshoot this issue?

I currently own a hybrid laney tf200, it is SS based for power section and 1 12ax7 for preamp

It has 2 gain channels,
channel 1 for milder distortion
channel 2 for heavier distortion

channel 1 works completely fine, it is able to get gain without any sort of disturbance,
channel 2 however has an intermittent signal (sort off) whereby I get distortion for a minute and then i don't at the next moment (still have sound, just dirty become clean)

I also noticed that i sometimes get intermittent signal loss when i walk to close to the amp.

Is this a tube issue or is it more of rusted components??

thanks!

 

[fifafu]

Let me take a lot at the schematic.

Hi any amp tech can help me troubleshoot this issue?

I currently own a hybrid laney tf200, it is SS based for power section and 1 12ax7 for preamp

It has 2 gain channels,
channel 1 for milder distortion
channel 2 for heavier distortion

channel 1 works completely fine, it is able to get gain without any sort of disturbance,
channel 2 however has an intermittent signal (sort off) whereby I get distortion for a minute and then i don't at the next moment (still have sound, just dirty become clean)

I also noticed that i sometimes get intermittent signal loss when i walk to close to the amp.

Is this a tube issue or is it more of rusted components??

thanks!

 

[fifafu]

Try changing tube, if not working check the opamp the is between boost channel and tube.

Quite a old amp...suspect cold joint as well.

 

[bkkcheesepie]

bro http://www.mif.pg.gda.pl/homepages/tom/files/TF200.pdf

which is the opamp chip i should replace??
I'm no electronic whiz and can't find the opamp symbol

 

[PatheinRaindropMoe]

op amp in the schematic is label as U#-TL072sm

There are more than 10 tl072 dual op amp in there and to know which one to replace, you have to trace the circuit. It is not a user changeable part and most likely to be soldered to the circuit board unless laney used ic chip socket for it.

In the schematic, footswitch jack label SK 3 and SW 2 are the switching portion for the channel, if wanna check, can start from there first, check for the connection those 2 parts.

If the channel switching portion is ok, then look at the op amp between the channels. TL 072 op amp is one of the most commonly found and cheapest op amp produced by different manufacturers. Even if unable to find the original one to replace, any generic tl072 op amp prolly will work as well as long as the pins are correctly connected to the rest of the circuit.

In the schematic, those tl072 op amp label as U# A and U# B means 1 single TL072 chip in physical.

anyway, iam not a qualified tech, but just know how to read the circuit and some prior experience to building and destroying stuff. Hehe, if you decided to diy, you be on your own.