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

baadc0de said:

I left the "unused" AOTs empty, should I replace them with wire links?

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no

baadc0de said:

The problems I'm having right now are pretty basic I think.. the left channel's VU goes "down" and pegsa, instead of "up" to center at 0. The right one pretty much centers at zero (both are with hold set at middle, link disabled). If I turn the hold knob I can get the left one to deflect a little, while the right one seems to have a pretty much healthy swing imitating my hold setting. Both VUs and hold pots are wired the same (I checked) as are the wires connecting the small attack/release boards to the main boards.

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The VU on mine is zeroed if hold is off (full clockwise) and then rises when hold is turned counterclockwise. I believe that's how it's supposed to be?

baadc0de said:

After some time (say one minute) the right one's VU starts oscillating a bit, i.e. the needle goes up and down like a metronome. I think it's about 60bpm.

I put some sound through the left channel, but in iron mode I'm not getting anything and in clean mode I'm getting sound that isn't dependent on the input sound or volume (input can be muted / non present / disconnected but it will still do this). It's kind of like a complex square wave with some additional stuff soperimposed on it. It's definitely "synthesized" sounding. I may record a clip of it. It's very quiet though, about -50dB on my interface.

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Recheck your wiring, probably somethings mixed up. If you can't figure it out you might brake thinks down into logical parts - check your input stage - check your output stage. Remove the compressor pcb from the audio circuit, connect only the out of the input stage with the in of the output and make sure it works as advertised etc...

Hope this helps a bit,

Michael

Thanks Michael,

it seems I actually populated some AOTs a lot of time ago that don't have to be populated (bought the PCBs 2 years ago, first ones I ever got... heh). Like AOT4, so I have to check what happens if those go away.

Okay thanks for clearing up things.. I connected the hold pot (a 10k lin) to the 3 pads on the attack/release PCB and removed the part with the rotary switch. I hope there weren't any additional links or connections there. If they are I think I could duplicate them. Hm. I'll take a look at the broken away part.

I have a modified Sifam meter pair that, when no voltage is applied to the meter rests at the bottom of the scale (the scale is horizontal). When I start with the hold centered, the good channel will rise to center on the VU scale and move up and down with the hold pot. Unfortunately, then it starts to undulate / oscillate after some time. The other one however, doesn't move up, but DOWN (which is very very weird) from zero to the minimum that the VU can deflect negatively (a few mm of course and it pegs).

Yup, I'll check the wiring .. again.. sigh.

The VU meters being mirrored, so are the wirings for them, sigh .. beginner mistake

I found out what the problem of the oscillations is.. the 317 heats up rapidly and then protect cuts out in waves. So that's the +28 rail crapping out. Interestingly, the 337 (-28 rail) isn't doing this. The 317 has maybe a bit worse contact with the heatsink, but I don't think it should affect it this much?? I'll try and find some of that thermal transfer material and lodge it there so that it will have better conductivity.

Aside from that, ideas? Why would the +28 rail be more hot than the -28 one?

EDIT: Also, is the output pot wiring correct like this: pin 1 minimum, pin 3 wiper, pin 2 ground (not connected in my case). And should the output pot affect the VU meter? It doesn't in my build.. the hold works "as expected" I think, that is, moving hold is moving the meter. Also, I have used trimmers to get both meters to center together on same hold value.

Thanks,
B.

Output pot shouldn't affect the meter.
Voltage regulators got overheated very fast on mine as well. I attached them to the case as a big heatsink (with mica insulators) and now it's OK.
I'm not sure whether the positive rail got warmer but it could be that some of the transistors (the big ones?) only use the posive rail?

Hi,

solved the voltage problem for now by improving contact with the 317 heatsink.

2N4898 gets much more warm than the other output transistor, so much so that I can't put my finger on it after a bit of warmup.

I did a bit of scoping..
- the input board gives out correct signal to the input board, however it has a cyclic DC shift to it of +- 0.4..0.6V (like a very low frequency AC has been superimposed on it, say, 10Hz or less)
- signal before the output pot seems to contain only this very-low-frequency AC

We'll see what else I can get later.. if anyone has an idea, don't be afraid to postulate some theories..

My unit now compresses - the VU meter reacts to input material, the hold knob works as advertised (very natural once you get the hang of it!) and attack, release, THD (bypass), lim/comp etc.. all seem to work with the VU meter as they should. It was a case of mirrored wire arrangement from the I/O board to the main board (insert homer d'oh!).

However, I get no sound through (except in hard bypass of course). At the output knob position on the main board I get only noise on pins 1 and 3.. I disconnected the pot to remove that from the equation and am using either a jump between 1-3 or nothing so I can test without the output section loading down. But there's only noise.. on shields of the output transistors and the output itself.

I'm a bit confused what may be the problem.. I'm obviously losing signal somewhere and it's not affecting the sidechain.

solder bridges or component shorting ?

Send a test signal thru and spot check half way thru the circuit ?

I always test my components before I solder them in

Transistor legs reversed by mistake ECB, CBE ? (TO-92 type) (TO-18) (TO-5,39)

any sockets being used ?

I'm sure you have considered the above but realizing simple errors are the ones
most likely .....

A few simple questions - I'm having trouble understanding how the power transformer should be connected to the power supply board. Do I need a 2x 25v power transformer? I'm uncertain about the ~ markings, I'm assuming they are supposed to indicate phase somehow?

Sorry I'm a newb. Also, I'm thinking about also building an insert controller and m/s stereo encoder/decoder into the same box. Does anyone know how much current a stereo TG limiter draws? I'm trying to decide if I should just use this power supply or build a new one I can draw more current from. I guess the amount of current that can be drawn is mainly limited by the regulators and choice of transformer, probably to some extent the diodes too.

Hi mate,

the ~ markings indicate where each leg from the power transformer connects to the PSU board. There is another point called CT where you will connect your center tap of the transformer. I think I used a 2x30V transformer.

Cheers,
B.

providedrailroad said:

A few simple questions - I'm having trouble understanding how the power transformer should be connected to the power supply board. Do I need a 2x 25v power transformer? I'm uncertain about the ~ markings, I'm assuming they are supposed to indicate phase somehow?

Sorry I'm a newb. Also, I'm thinking about also building an insert controller and m/s stereo encoder/decoder into the same box. Does anyone know how much current a stereo TG limiter draws? I'm trying to decide if I should just use this power supply or build a new one I can draw more current from. I guess the amount of current that can be drawn is mainly limited by the regulators and choice of transformer, probably to some extent the diodes too.

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baadc0de said:

Hi mate,

the ~ markings indicate where each leg from the power transformer connects to the PSU board. There is another point called CT where you will connect your center tap of the transformer. I think I used a 2x30V transformer.

Cheers,
B.

providedrailroad said:

A few simple questions - I'm having trouble understanding how the power transformer should be connected to the power supply board. Do I need a 2x 25v power transformer? I'm uncertain about the ~ markings, I'm assuming they are supposed to indicate phase somehow?

Sorry I'm a newb. Also, I'm thinking about also building an insert controller and m/s stereo encoder/decoder into the same box. Does anyone know how much current a stereo TG limiter draws? I'm trying to decide if I should just use this power supply or build a new one I can draw more current from. I guess the amount of current that can be drawn is mainly limited by the regulators and choice of transformer, probably to some extent the diodes too.

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Oh okay that makes sense ha ha. I feel stupid now. Well on the board layout one was marked '25' and one was marked '1', and I didn't see where the Center tap was supposed to go. Did you use a 3A transformer since the regulars can draw up to 1.5A a piece?

TG PSu requirement is +/- 28v output

Use 56-60vct (2x28vac) or (2x30vac) /30-50va transformer

Mark called it first.

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I think it was on the first page of this thread

Now if only someone can  measure current how much current the limiters draw for me I will know FOR SURE whether I need to redesign my power supply, ha ha. I guess I can just use 24v linear regulators with PNP power transistors to increase output current

providedrailroad said:

Now if only someone can  measure current how much current the limiters draw for me I will know FOR SURE whether I need to redesign my power supply, ha ha. I guess I can just use 24v linear regulators with PNP power transistors to increase output current

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Use LM317/337 pair they will supply 2 channels with no problems

Well, like I mentioned earlier in this post I'm running some Relays and Lighted Switches and a Mid Side Stereo decoder off the same supply. I just modified the existing design with darlington PNP pass transistors on the positive rail, added a 18v regulator for the M/S supply and laid out a new circuit board. Everything is good on the power supply front.

Last question. The molex connectors used - will I need special tools to make cables for these? They use normal .1" spacing, correct? And the switches - they are just normal size PCB mount, not mini or submini? Ordering for this project without having the boards in person yet is a little frustrating. I wish there was better documentation.

I just strip the wire and crimp mine manually with a pair of long nose pliers. Then I flow a little bit of solder into the join to make it extra tough

No fancy tools required... if you had to do 1000s of them then you might want a tool, but for one offs I find the manual method totally fine.

If you look around on synth diy forums there's probably a detailed explanation with photos out there somewhere...

EDIT: this is advice for the crimp types - there's also IDC types that work a different way... you can get a cheap plastic tool for these though - might even be easier...

I am also running a bunch of relays with my power supply,  I don't think you will have a problem with the LM317/337 combination.  If you are worried you can easily calculate what all the relays are pulling using ohms law, & the lamps using ohms law & P=IV.


I used to crimp with pliers & solder, but I bought a proper crimp tool several years ago,for £10 & the connections I now get are vastly superior to what I was doing before, much quicker to make with no soldering is required.  For £10 it's worth every penny in my view.

Hey Rob - that does sound worth 10 quid.... do you have a link to the tool you bought?

haima said:

Hey Rob - that does sound worth 10 quid.... do you have a link to the tool you bought?

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OK gone up a bit in price but still worth the cash http://www.rapidonline.com/Tools-Equipment/Ratchet-Action-Crimp-Tool-Ht225d-85-0262/?sid=beb63ebc-e413-4328-81ef-0e0a754ec748

thanks mate!

have'nt posted here in a while ........

Q : has anyone been able to locate a source for the original HS2051 Zener Diode for the TG Diode bridge ?

Currently all that is available is the 1N751A which is also a 5v1 Zener diode. The HS2051 seems
unobtainable and no datasheet exits thru normal www searches. Apparently the HS2051 part #
is also used in a digital chip which is 100% unrelated to the diode and the TG limiter.

There are other 5v1 zener diodes available too , ex : BZX850, but it seems the basic operating
voltage is of little concern with the diodes base line character compared to the 1N751, in other words
no noticable difference in audio quality.

Also , is there a source for the original TG layout ? not he Fester unlimited version.