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

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imo said:
wow. Thats a pretty big disparity. Looks like Igor went up from an 82k to 100k. Definitely see the 8.2k

Fo sho.  I'm not qualified to actually determine what effect the difference would have - or even posit a guess for that matter...  anyone else?  All of the other values in that area of both schems seem the same.  I wonder if it is intentional or a mistake?  I'd think if Igor changed it for the 500 version it was intentional...

I'm gonna leave the 82k's I already soldered in there stay until I hear differently...

 
Okay - I feel like this maybe the dumbest question I have asked on this board...  Is the switch for the Iron/Bypass/Clean is a SPST?  I am planning on going with the 1:1/Trafo Bypass setup - although I will add the iron later.  How would a SPST switch accomplish 3 things?!  Or do you sacrifice hard bypass by having iron/no iron switching?  I've looked over the various BOMs, Bypass Schem and Bypass Versions PDF and I am as confused as ever!  Time for lunch I guess...

Thanks!

 
You can build with opt out stage and use Clean or Bypass position on switch, Iron will work after you add transformers
 
JdJ said:
Okay - I feel like this maybe the dumbest question I have asked on this board...  Is the switch for the Iron/Bypass/Clean is a SPST?  I am planning on going with the 1:1/Trafo Bypass setup - although I will add the iron later.  How would a SPST switch accomplish 3 things?!  Or do you sacrifice hard bypass by having iron/no iron switching?  I've looked over the various BOMs, Bypass Schem and Bypass Versions PDF and I am as confused as ever!  Time for lunch I guess...

Thanks!

The bypass schematic is somehow confusing. You need a 3 position ON-OFF-ON switch to have  iron, opamps and real bypass.
 
Thanks guys!
peskado said:
You can build with opt out stage and use Clean or Bypass position on switch, Iron will work after you add transformers

Exactly my plan - glad it should work.

Majestic12 said:
The bypass schematic is somehow confusing. You need a 3 position ON-OFF-ON switch to have  iron, opamps and real bypass.

See?  I knew I was missing a simple explanation! :p

Cheers!

Josh
 
hi
i attached some bc214 datasheet (partial)
include the motorola that seem to be wrong ,
(don't confuse the motorola bc214 with bc214L)

image 1- motorola bc214 "wrong" pins order

1bc214motorolawrongdoc.jpg



somebody have checked about right pins order ?
peace!

ps
motorola semiconductors email not found
any info about is welcome.  ;)

Rob Flinn said:
Maybe you already got asked this but did you use the right version of the BC214 ?  There are 2 different pin outs for this transistor.  The pcb has the ebc pins marked.  If you bought the BC214L (I think) then the pin outs will be wrong & you will need to turn them round.

If you have the right ones then please ignore the above !

You can check the V's on the transistors in a basic way by checking that there is around 0.6v between base & emitter.  But this may not hold true for all configurations.
 
One interesting problem for the crowd here, maybe someone has any ideas..

Sometimes, when excessive low frequency information is in the input (such as from a preamp when recording a kick drum or direct bass guitar) and the gain reduction is set to a slow enough attack and quite a bit of makeup, the TG1 starts smoking R77. Could the output transistor pair be somehow to blame? I don't know enough about transistors, but say if one of them faults into being a straight line for a time?

It all works out if I power it off for some time. The output transistors are not heatsinked, maybe I should do that?

Thanks!
 
baadc0de said:
One interesting problem for the crowd here, maybe someone has any ideas..

Sometimes, when excessive low frequency information is in the input (such as from a preamp when recording a kick drum or direct bass guitar) and the gain reduction is set to a slow enough attack and quite a bit of makeup, the TG1 starts smoking R77. Could the output transistor pair be somehow to blame? I don't know enough about transistors, but say if one of them faults into being a straight line for a time?

It all works out if I power it off for some time. The output transistors are not heatsinked, maybe I should do that?

Thanks!

Ha! welcome! You're not alone. I've been mentioning this problem for quite a while but unfortunately it looks like a mystery :)

http://www.groupdiy.com/index.php?topic=37400.msg512287#msg512287
http://www.groupdiy.com/index.php?topic=48297.msg617261#msg617261

I'm pretty sure it's not a heat problem as I'm using heatsinks on the transistors. What transistors do you use?
What wattage is the 56ohms resistor? Do you have good heatsink on the PSU regulators?

In my case a 2watt resistor with a BIG heatsink on the regulators gives me a maximum of around 40C which I suppose it's OK.

Still though, I don't know what causes it.  ::)

Good luck and let me know. It's been my nightmare for more than two years now  ;D
It'll be good if other people can report too.
 
Quick question - do you'all think a utc a-20 would be a good candidate for the output transformer.  The data sheet says it can be a 600 pri and 600 sec.  I'm running my unit 1:1 per Uncle Festers docs...

any thought?

Lovin this thing on Drum rooms and guitars, I think I'm using it too much  :)


 
Great to know it's not that uncommon...!

I have for now put two philips BC capacitors (1000uF) in antiseries, which gives about 500uF of capacitance but blocks DC both ways. I'll let you know if it helps any.. the output transistors are NOS Motorola ones from electrochronic as are the rest of transistors.

The reason to put in another capacitor - a fake bipolar one - is because in the previous configuration it smoked not only R77 but also a winding on the output transformer (which now reads open). So this is more intended to protect the trafo. If anyone came to a solution to this, please let me know!

warpie said:
baadc0de said:
One interesting problem for the crowd here, maybe someone has any ideas..

Sometimes, when excessive low frequency information is in the input (such as from a preamp when recording a kick drum or direct bass guitar) and the gain reduction is set to a slow enough attack and quite a bit of makeup, the TG1 starts smoking R77. Could the output transistor pair be somehow to blame? I don't know enough about transistors, but say if one of them faults into being a straight line for a time?

It all works out if I power it off for some time. The output transistors are not heatsinked, maybe I should do that?

Thanks!

Ha! welcome! You're not alone. I've been mentioning this problem for quite a while but unfortunately it looks like a mystery :)

http://www.groupdiy.com/index.php?topic=37400.msg512287#msg512287
http://www.groupdiy.com/index.php?topic=48297.msg617261#msg617261

I'm pretty sure it's not a heat problem as I'm using heatsinks on the transistors. What transistors do you use?
What wattage is the 56ohms resistor? Do you have good heatsink on the PSU regulators?

In my case a 2watt resistor with a BIG heatsink on the regulators gives me a maximum of around 40C which I suppose it's OK.

Still though, I don't know what causes it.  ::)

Good luck and let me know. It's been my nightmare for more than two years now  ;D
It'll be good if other people can report too.
 
Yes, let me/us know please.
I'm pretty sure we are not they only ones who have this issue.  ;)
 
warpie said:
Yes, let me/us know please.
I'm pretty sure we are not they only ones who have this issue.  ;)

And it looks from your other post that this DC/hot resistor occurs with an output transformer as well as without one correct?

 
Yes, with or without transformer. Also, with transformer, it occurs both with gapped and ungapped.

EDIT: Speaking of transformers, am I right to think that an ungapped transformer will be more appropriate for this project?

 
warpie said:
EDIT: Speaking of transformers, am I right to think that an ungapped transformer will be more appropriate for this project?

That's my understanding, but if you have a bunch of DC on the output before the OT perhaps a gapped would be better?
 
dirty1_1garry said:
Hi
While my TG in process want to ask you. What is the switch LIM/THD?! What it does?)

Disables the side chain, thus turning compression off, but leaving the rest of the circuit in the audio path. Similar to 1176's off setting, where the input and output amps are still in circuit and can be overdriven, but no GR is happening.
 
JdJ said:
imo said:
wow. Thats a pretty big disparity. Looks like Igor went up from an 82k to 100k. Definitely see the 8.2k

Fo sho.  I'm not qualified to actually determine what effect the difference would have - or even posit a guess for that matter...  anyone else?  All of the other values in that area of both schems seem the same.  I wonder if it is intentional or a mistake?  I'd think if Igor changed it for the 500 version it was intentional...

I'm gonna leave the 82k's I already soldered in there stay until I hear differently...

The reason R47 is 82K and not 8.2K is because the attack switch was added which was not part of the original circuit. The switch has 10 resistors that are in parralel with R47 and you get the following values.

TG12413_attack_times.png


As you can see position 7 is 8.19K which is the same as the original.

And the release times.

TG12413_recovery_times.png


Regards,
Brezo
 

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