Re: TG1 - advice from any one who has built it...
« Reply #820 on: March 03, 2019, 07:55:15 AM »
i think its time to throw the towel. i just dont get this thing working as it should . without a reference im lost.
now, is there anyone who could help me here in the eu? anyone with a working unit, that could maybe troubleshoot one board for me? i dont have a fortune left - but i can pay. i invested too much to give up on this. any help is appreciated. cheers

Re: TG1 - advice from any one who has built it...
« Reply #821 on: March 05, 2019, 05:35:18 AM »
ok - i dont get any feedback. darn im too late with this build. perhaps someone can still try to answer me some questions:

- should AOT10 have an effect with no input signal and no compression?  or is this AOT just working under hard compression?
   my AOT10 just doesnt do anything. i can balance with AOT7 but AOT10 has no effect. then again this AOT is wired compreletly
   different than in the original schematic.

-could my problems stem from low hfe from my transistors? im just running out of ideas and my hfe is rather low. they are all around 180-250 hfe. all pairs  are matched.

- i have an extra ground wire running to the psu from my starground. is this the way to go, or should the psu receive its ground
  via the mounting screws only? did you guys connect your PE cables?

- my 10v going to the hold switch do not stay constant. it varies between 10v (0 hold) and 9,6v (full hold). is this ok?
« Last Edit: March 05, 2019, 07:32:49 AM by salomonander »

Re: TG1 - advice from any one who has built it...
« Reply #822 on: March 05, 2019, 09:01:53 AM »
to state my problem again:
full hold does bad things. the needle gets jumpy and the compressor over sensitive. when switching from full hold to a lesser position the needle jumps and i hear a click. the unit also gets slightly hummy with full hold. when im in THD mode the last step on the hold switch gives me a big gain increase compared to the others. i also hear that click in THD mode when i switch back from full hold. and lots of the parts (everything around VT5 & VT6) make my vu needle jump when touching them with my test probe (not earthed just going to my fluke). this doesnt happen in any other hold position.

also the voltage going from VT3 and VT2 to the sidechain kind of flips in the last hold setting.
they always stay around -9v. but on full hold the voltages mess up. collector of VT2 goes to -6v while collector of VT3 goes to -12v. i can somewhat balance this out by AOT7. the needle gets a more stable then - but its still not right. removing the zener diodes keeps the voltage stable even on full hold.

and no effect from AOt10 nor unity gain with hold in the middle.

PS: actually AOT10 does a tiny bit. when hold is fully off it does +-0.3Vdc. with hold in the middle it does +-.01 and nothing with full hold.
« Last Edit: March 05, 2019, 03:47:42 PM by salomonander »


Re: TG1 - advice from any one who has built it...
« Reply #823 on: March 07, 2019, 07:54:24 AM »
Due to popular demand, please find attached a working LTSpice simulation of the TG1 compressor for educational reference.
I gave this model to previous forum member Bruno2000 in order to help him debug his build.

It might be useful for people to play with and get an idea about the voltages and currents to expect at various points in the circuit.

If for whatever reason this is inappropriate, please, by all means, remove this post.

I hope it helps some people!

Change the extension to .asc to load it in LTSpice.

Re: TG1 - advice from any one who has built it...
« Reply #824 on: March 07, 2019, 08:15:25 AM »
thanks a lot i really appreciate it! best


Re: TG1 - advice from any one who has built it...
« Reply #825 on: February 24, 2020, 12:04:01 PM »
The left channel on my DR-ZEN2 sadly died. There is no output signal, however, the gain reduction needle correctly reacts to the incoming signal. If I switch to THD mode and turn the input to the max I'd hear some of the input, but very faint and distorted.
Everything looks okay, no evidence of burnt parts or cold solder joints. I removed and checked power transistors (2N4898 and 2N4910 and they are fine). I checked two other transistors near those and they are fine too.
I also checked the output transformer and it is fine.
I noticed that 2N4898 gets noticeably hotter than the same one on the working channel.
I am also not sure what could have caused it.
I am writing maybe someone had similar problem and can recall it.
Worst case scenario I will have to pull parts one by one and test them, probably starting with semiconductors.
If I find the fault I will definitely update.


Re: TG1 - advice from any one who has built it...
« Reply #826 on: February 28, 2020, 06:11:12 PM »
I couldn't find anything so I started staring at the board... Then I found a little scratch just next to the power transistor mounting hole. That scratch was the ground and it seems like as time passed somehow connection from transistor was created and it was shorting to ground and not passing signal through. I put a plastic washer underneath the transistor and it now works fine!
Can't find other explanation  :o


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