[BUILD] fripholm's TG1 Zener Limiter boards - support thread

[JCN1218]

Tried putting signal right into that middle pad of the bypass 2 section. Still nothing  I guess there must be a problem in the output stage. There must be one in the output stages of both boards too, because the second board is experiencing the same problems. I looked at the schematic for the output stage. If Q12 or Q13 were installed backwards, would that be possibly causing my problems? I'm using the BD139&140. I remember during install having some trouble figuring out which way they should be placed, especially the BD139. It's the only thing I can think of right now as far as trouble shooting is concerned.

 

[fripholm]

The three dots/notches on the BD139/140 should be facing outwards. Look at the photo in the guide, top of page 5.

 

[JCN1218]

Well, the 139 was indeed backwards. It's now oriented correctly. Unfortunately, it hasn't solved my problems. I'm still getting no output, even when directly sending the signal to the middle pad of bypass 2.

I'm not sure what else could be wrong at this point. Thanks for everyone's help so far, please let me know if you have any ideas as to what else might be wrong.

 

[fripholm]

I'm pretty sure you have done this before, but just to be sure: check the orientation of all the transistors, diodes and polarized caps. Make sure the NPN and PNP transistors are in their correct spots, Qxx are PNP (BC559, 560 etc.),  Txx are NPN (BC550).

Try to fix the output stage first. It's a pretty simple circuit block with just a handful of parts.

What's the voltage at the top (+) of C29? It should read about 12 Volts. Maybe something burnt out due to the incorrectly installed BD139...

 

[JCN1218]

Yeah, the first thing I did once I saw it wasn't working was to check my transistors.

I did just do a quick test on the top of C29 and I'm not getting a DC voltage reading at all really, so something must have burned up due to the flipped BD139. Now I just have to track down the malfunctioning part(s). I haven't seen any smoke or anything during any power ups so far.

 

[AD797]

omg... the transfomer i got are that big!!!

 

[MrBlomski]

What are these monsters?

 

[AD797]

it´s a Sedlbauer LÜ81, it´s 8:1, 4:1 and 2:1 in one monster...

 

[Murdock]

Hey, sorry if this has already been asked. But what would be the drawbacks of using a 24V PSU instead of the 28V?
I have a really good 24V PSU which I use for a lot of my modules. Would be great if I could also use it for this compressor... Could I make any changes to the circuit to accommodate a 24V supply?

 

[fripholm]

Could I make any changes to the circuit to accommodate a 24V supply?

I don't know your 24V supply, but maybe it's easier to modify your PSU's circuit to deliver the 28 Volts?! If it's based on linear regulators, the output voltage is just a matter of a couple of resistors or maybe there's even a trimmer...

 

[Murdock]

I don't know your 24V supply, but maybe it's easier to modify your PSU's circuit to deliver the 28 Volts?! If it's based on linear regulators, the output voltage is just a matter of a couple of resistors or maybe there's even a trimmer...

Hey, thanks for the fast reply!
But I don't want to modify my 24v supply as I Use it for most of my German broadcast modules which need 24V... so I assume It's not a good idea to run the TG1 with 24V then? Probably less headroom, right?

 

[fripholm]

Hey, thanks for the fast reply!
Probably less headroom, right?

That would be one thing. There are also transistor regulators on board that provide another bipolar +/-20Volts for the compressor stage to work properly.

 

[Potato Cakes]

So the power transformer is on backorder, even though I was certain it was in stock when I ordered from Allied. So unless I want to wait a month, I'll have to find something else.

Curious to see if other people have this up and running yet.

Thanks!

Paul

 

[Ilya]

I have the 2x24V 0.5A transformers in stock if you need it.  I'm using them for my 12413 modules.

 

[Potato Cakes]

Thanks for letting me know. I'll keep this in mind if I get stuck.

thanks!

Paul

 

[fripholm]

Yes, someone pointed out the other day, that a 2x24V power transformer would also work in this case.

Curious to see if other people have this up and running yet.

Yup, me too!  ;D

 

[Potato Cakes]

Hammond Power transformer ordered from mouser. Should be here in a couple of days. I will report back after calibration.

Thanks!

Paul

 

[Mike Havok]

Hi people, just got my boards today (christmas present from my wife)

I was wondering, is there a way of increasing the treble boost in the input stage? Either with a switch or pot?

Really looking forward to getting stuck into building this (thanks Thomas!)

 

[fripholm]

I was wondering, is there a way of increasing the treble boost in the input stage? Either with a switch or pot?

I'm glad, the boards made it in time before xmas

You could make R1 and C3 switchable for different options. With the given values it's only a slight boost - about 1dB at 20kHz, originally intended as 'frequency correction' according to the circuit description of the original.

 

[Potato Cakes]

So I'm having a bit of trouble trying to get power to the relays I'm using for to do the switching and LEDs for the push button DPDTs. It seems that when I try to put a diode (1N4148) across the contacts that receive power it burns up the 22R resistor on the PSU. I guess I can just wire the relays without the diodes but I thought it was go practice to do so for circuit protection. The diode was wired with the anode on the +V side and the cathode to the side connected to ground. I don't recall having this trouble on other builds.

Thanks!

Paul