TG1 - advice from any one who has built it...

[salomonander]

hey there,
i really hoped i would not have to bump this again - but i do. i took a long break from this and finally wired and fired this thing up. most things work as they should, but the hold control does not do what its supposed to. maybe one of you has an idea. i had to wire all switches by hand since the pcb did not fit my frontpanel and im pretty sure i messed up somewhere in there.

when fully engaging the hold switch (i used a 1x12 switch) the unit works  as i would it expect to. but when lowering the hold, the level drops and the vu meter shows increased reduction (regardless of input level). it still compresses - but only the spikes above the static reduction shown on the meter.  when no signal is applied at the input and hold fully deengaged, the vu meter reads full reduction which then dops the further i engage the function. this also happens in thd mode.

anyone have an idea? i was confused regardig wiring the hold switch since igor released that "tg fix"  document and the original shematic seemed wrong. i did redraw the shematic accordingly. but maybe i did that wrong? i'll attched my version of the shematic to this post. the hold schematic is at the bottom right. maybe someone could be so kind and take a look? maybe i redrew it incorrect. ill attach the emi shematic too.

if ayone has an idea where i might have messed up - any help would be apprecited. im scratching my head. i most likely shorted something that is not supposed to have a connection. but what ?

thanks!

ps: could a reversed or broken D12 explain the behaviour?
        R115 is jumped

 

[salomonander]

this is the original emi shematic:

 

[salomonander]

just noticed that the lower the signal i feed - the more compression i get

 

[Ilya]

Well, until I saw your last message I was going to say that that's the correct behavior.
When you turn the hold one side you get higher output level and more compression. When you turn the hold another side you get less output level and less compression. You last message puzzles me though. I can't understand how you can get more compression by lowering the level.

 

[salomonander]

Well, until I saw your last message I was going to say that that's the correct behavior.
When you turn the hold one side you get higher output level and more compression. When you turn the hold another side you get less output level and less compression. You last message puzzles me though. I can't understand how you can get more compression by lowering the level.

hey thanks for the rely. maybe its correct after all? but it behaves so akward. when i disengage the hold pot, the meter reads full reduction and i hardly get any signal going through..... is that normal?

ps:  yes, the reduction gets a lot more obvious when i lower my input signal. half the signal input and every kick drum seems to trigger the unit more than before.

ps2: my fast/slow switch seems to affect the release and attack both. is that normal?

 

[weiss]

hey thanks for the rely. maybe its correct after all? but it behaves so akward. when i disengage the hold pot, the meter reads full reduction and i hardly get any signal going through..... is that normal?

ps:  yes, the reduction gets a lot more obvious when i lower my input signal. half the signal input and every kick drum seems to trigger the unit more than before.

ps2: my fast/slow switch seems to affect the release and attack both. is that normal?

seems to be normal
the fast / slow has influence on the two settings

 

[salomonander]

seems to be normal
the fast / slow has influence on the two settings

thanks, just to clarify: yes (normal) in regards to "ps2" (fast/slow) or my entire issue? cheers

 

[weiss]

it is normal if you pull the hold pot completely to one side, that more compression appears and therefore levels change, on the other hand if you engage the fast/slow switch, it affects both, release and attack time constants.

i quote from the manual

The Hold control RV1 is a 10K linear potentiometer. It is fed through R63
from the point which is decoupled from the +20V supply by R45, 016, and which
feeds the collector of VT17 and the emitter of VT21. This results in the upper end
of the Hold control being at about +10V. The potential from the slider is connected
via D12 to the junction of D11 and R47. Thus the Hold control sets a potential
below which the effective control voltage cannot fall. This detennines the increase
of gain with falling signal level, and henoe controls the amount of compression or
Iimiting.

The earthy lead from the Recovery switch is taken to the slider of the Hold
control so that the discharge of C18 is exponential to the potential on the slider.

Terminal 36 is connected to a ganging switch. When this is switched to the
‘gang’ position this terminal is connected to the corresponding terminal of the
limiter in the other channel of the stereo pair. In this condition both units are
controlled by whichever control voltage is higher, and the Recovery controls should
be set to the same setting.

 

[salomonander]

hey weiss,
thanks a lot. ill study what you have attached. i always need a little longer for this but there is certainly something wrong. when i feed a low signal i can clearly hear the attacks triggering the compressor in my signal. i hope i explain it right ... but i can hear the impulses that are supposed to feed the compressor mixed in with my signal on the xlr outs. that cant be right. i need to figure this out. most likely a short somewhere.

 

[Rob Flinn]

What you describe sounds normal to me.  WHen you operate the hold control the meter displays a static level & any compression that goes on is superimposed on that static level.

It is worth saying that this compressors controls are weird & it  drives differently to any other compressor I have.  I 

 

[weiss]

hey weiss,
thanks a lot. ill study what you have attached. i always need a little longer for this but there is certainly something wrong. when i feed a low signal i can clearly hear the attacks triggering the compressor in my signal. i hope i explain it right ... but i can hear the impulses that are supposed to feed the compressor mixed in with my signal on the xlr outs. that cant be right. i need to figure this out. most likely a short somewhere.

maybe there is a bleed somewhere? did you already check for continuity where there shouldn't be?

What you describe sounds normal to me.  WHen you operate the hold control the meter displays a static level & any compression that goes on is superimposed on that static level.

It is worth saying that this compressors controls are weird & it  drives differently to any other compressor I have.  I

that is true indeed. you have to get used to it. not straight forward like an ssl

 

[salomonander]

maybe there is a bleed somewhere? did you already check for continuity where there shouldn't be?

thats what im about to do. if you happen to have an idea where to look first, go ahead - im a noob
or hold on - doesn't a compressor work with reversed phase somehow? (such a noob) could i have messed tis up by wiring my sidechain reversed?

 

[salomonander]

ok so since i did not know what to do i simply went through the test voltages found in the original shematic.
and i certainly have wrong voltages. most of them are fine. except for VT5 and VT6 and the surrounding negative voltages. collector of VT5 should be -26V (testpoint T_B on Igor) and emitter of VT6 should be -10,7V. now collector of VT5 gives me +10,5V and emitter of VT6 is +6,5V. im having no negative voltages there. im also getting these 6,5V on the diode D5 (across meter) instead of -16,8V. no meter connected.

so now im lacking the basic electronics skills. what could prevent that negative voltage from happening? where is it created? am i looking for a broken transistor around VT5 & VT6?

 

[Ilya]

These negative numbers around that part of the circuit are NOT voltages. It's signal level at that point.

 

[salomonander]

These negative numbers around that part of the circuit are NOT voltages. It's signal level at that point.

thanks. but are you certain about this? except for that part of the schematic, all other test numbers show up for  me in dc on my multimeter. cant be coicidence...
or do you mean all numbers missing a V for voltage?

 

[Ilya]

Yes I am. I traced the signal through my unit and got those values (or pretty close to them).

Edit: generally, all numbers with dots before them are AC signal voltage, most "-xxx" numbers are dBu values of the signal. In the sidechain there are some DC voltage readings, but in the input section it's almost everything AC.

 

[salomonander]

it works after all!!
gosh what a massive pain in the butt. i did draw the schematic wrong. the auto release caps were connected to the wrong side (they need  to be joined with  R107 instead of R106 -  rest as on my schematic). plus i had a short on one of my release switches. but now both channels work as they should.

it might be a stupid question after having all these issues. but could anyone think of a simple mod that would turn the hold switch into a regular threshold? no more messing with the level or vu meter? i'd much prefer that honestly.

 

[Rob Flinn]

it might be a stupid question after having all these issues. but could anyone think of a simple mod that would turn the hold switch into a regular threshold? no more messing with the level or vu meter? i'd much prefer that honestly.

If you have Igors documentation it explains how to do this jumpering etc on the i/0 board.

 

[weiss]

it works after all!!
gosh what a massive pain in the butt. i did draw the schematic wrong. the auto release caps were connected to the wrong side (they need  to be joined with  R107 instead of R106 -  rest as on my schematic). plus i had a short on one of my release switches. but now both channels work as they should.

it might be a stupid question after having all these issues. but could anyone think of a simple mod that would turn the hold switch into a regular threshold? no more messing with the level or vu meter? i'd much prefer that honestly.

I'm glad you figured it out!

 

[salomonander]

If you have Igors documentation it explains how to do this jumpering etc on the i/0 board.

hey,
i do have all the documents. but not really an idea on how to go about it. could you maybe elaborate. i do know where everything goes on the boards - i lack the engineering knowledge.