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

[late]

Thanks SLB. What transformers people have used? I've looked sowter, edcor and carnhill transformers. Carnhill VTB9071 input and VTB2280 output for 1:1 setup. Should work well? Sowter is more expensive and maybe is edcor too cheap or are they good?

 

[jplebre]

Hey guys, just confused about something
A lot of people seem to have trouble with the hold switch, Since this is 10 resistors for 11 positions (position 1 is 0ohm)  and is 10k linear, shouldn't it be 1k resistors per step?

1- 0
2- 1k
3- 2k
4- 3k
5- 4k

- 6- 5k -

7- 6k
8- 7k
9- 8k
10- 9k
11- 10k

?

 

[late]

Hey guys, just confused about something
A lot of people seem to have trouble with the hold switch, Since this is 10 resistors for 11 positions (position 1 is 0ohm)  and is 10k linear, shouldn't it be 1k resistors per step?

1- 0
2- 1k
3- 2k
4- 3k
5- 4k

- 6- 5k -

7- 6k
8- 7k
9- 8k
10- 9k
11- 10k

?

Hi

http://twin-x.com/groupdiy/displayimage.php?album=325&pos=4

Hold values are marked on that schematic file.

 

[jplebre]

Hi Late!! Ty!! I thought I had downloaded everything from that page.

Hmmm These values look more like Log ladder to me and do explain why Rob Flinn said he could only get to 9.67k earlier this post.
What did people go with for the 10k hold option?

@Late, I'm going edcor for input, VTB2280 for o/p. I've used Edcors on my LA2A's and they are pretty good, specially for the price!!!
R115 is either jumped for 10k hold or 5k for 5k hold.

Cheers
J

 

[late]

Is it possible to use 21step switch? And can i use 10k pot with it if i have did hold fix for the panel pcb. Or do i need remove that fix?

 

[peskado]

im used 21 step for hold
20 x 499ohm

 

[jplebre]

im used 21 step for hold
20 x 499ohm

I might upgrade to that at some point. Too expensive as it is at the moment.

 

[jplebre]

Is it possible to use 21step switch? And can i use 10k pot with it if i have did hold fix for the panel pcb. Or do i need remove that fix?

the fix is for hold - either Pot, 11 position or 21. Just break off the PCB and replace.

 

[peskado]

im used uraltone)

 

[late]

So step 1 is 0ohm and everyone from 2-21 are 499ohm?

 

[peskado]

yes, 2-21 499ohm, total 10k

 

[jplebre]

That's why I was confused as the other values you said earlier was more of a  logarithmic aproach - when it should be linear.

I'm populating Igor's PCB with the suggested values on the schematic, and I got a few lorlins where I'm populating with 10x 1k and I'll try both see what feels better.

 

[late]

Original unit uses 21 position hold switch? I tried to google but can't find what values.

 

[jplebre]

original uses pot I belive

 

[late]

original uses pot I belive

First 1969 version uses switch. But can't find what kind switch.

 

[jplebre]

Right guys need a bit of help here. I'll try to write it so you can teach me how to fish, rather than just blurb out an answer.

Both channels populated at same time. Voltages check @supply points, jumpers done so +20 is reading +20, -20 is reading -20.30 (very close for both channels).

Symptom: both channels have a huge drop in level, of about 20 dB if hold set to 0 and O/p set to 0. O/p to +10 and hold to +10 will almost bring the signal to "level).

I traced the signal through the pad where it drops aprox. 9dB. (eg. a .750v signal drops to .230 ish). Signal reacts to hold changes on TPC and B. tracing the signal to the S3 pad it never boosts the 9dB it should in VT9.
But maybe I'm doing it wrong. Where should the signal get boosted? at collector of VT10, VT9 or VT8?

So signal reaches S3 at 222v or lower.

With no signal present, the voltages match the dribbles done by igor on the "resharpened cooking recipe" schematic (+-1v in some places).

Hold is a 9.4v measure at point 6 of the jumper. But this drops in level as hold goes down. I thought that that was a constant potential and only the wiper should change the voltage?

Any help would be grand!

 

[jplebre]

To make things more interesting - seems gain is kept on THD mode.
So issue either on sidechain (Aot1?? earlier? can't really tell how to troubleshoot this as it's a feedback compressor) or Vt8/VT10/VT9 issue?

Ideas?

 

[imo]

hello,
I am finally getting my TG1 500 going. There are a few differences with the 500 from the rackmount, but fundamentally is the same.
I am good on my +20 points, and my VT4-5 are balanced. The unit seems to be working properly. I am having a weird issue with the relays however. They are set to default to bypass, but when i short the "bypass" switch to pull the circuit in, the switch still stays in bypass. I can hear the relay clicking a little, but it doesn't seem to throw the switch. I have temporarily pulled them out of circuit to check the rest of the unit, and from what i can gather it is working properly. I am able to see the affects of adjusting hold, input output, etc.
Before is start tearing this thing apart, does anyone have any obvious points to check?
the lm317 seems to be working, but the measurements seem quite off. 16vDC at input, adjust is -11.55, and out is -5v
I am using a 3.9k resistor as the adjust. Also i have tried replacing both the .1cap and the 4148 diode. When i first replaced the diode i briefly had -16v on both sides, but now i am back to -11.55 on cathode side and 16 on anode.. are my 4148's faulty, or does this sounds like the 317?
Thanks
Ian

 

[bruno2000]

Is the relay coil resistance greater than 700 Ohms?
Best,
Bruno2000

 

[Harpo]

the lm317 seems to be working, but the measurements seem quite off. 16vDC at input, adjust is -11.55, and out is -5v
I am using a 3.9k resistor as the adjust. Also i have tried replacing both the .1cap and the 4148 diode. When i first replaced the diode i briefly had -16v on both sides, but now i am back to -11.55 on cathode side and 16 on anode.. are my 4148's faulty, or does this sounds like the 317?

I am not building this unit, but from schematic the LM317 is not set up as a voltage regulator but for a [1.25Vref/3K9]=0.32mA constant current regulator. 0.32mA won't operate your relais coils, so this 3K9 is way too high.