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

[e.oelberg]

here is a pic of my beauty. each channels runs fine. If I connect both to the psu I have a ground hum. It must be some small stupid mistake


nicholas

 

[briomusic]

If you leave off the bypass boards and just run the main boards in unbalanced mode, do you still have the same problem? With the bypass boards connected, does it happen in clean and iron mode?

 

[e.oelberg]

it"s in clean and iron mode, I disconnected all irons  with no change running unbalanced with same result. If I disconnect the psu from one board, the other one is clean !

 

[briomusic]

ok cool, but what I mean is disconnecting the entire balancing/bypass board and use the unbalanced in and out on the mainboard, just to narrow down the problem to a specific pcb.
by the way, I see you have all four power pins connected, I am not sure if I remember correctly, but I think one is audio ground, the other chassis ground or similar. I only have one (the audio) ground connected, this might be something worth trying for you too.

 

[e.oelberg]

the problem is on the main board. I run in unbalanced direct into the board. It"s before the last  amplification stage before he output pot

 

[wmtunate]

Are you sure it's ground hum?  I had a similar problem because of voltage sag dropping the PSU out of regulation, causing a buzz/hum.  That would be consistent with you having to run both boards before it starts.  What are your toroid specs?

 

[e.oelberg]

well thats a good hint, the toroid seemed a bit stressed

 

[jackies]

Are you using LL1517 both on input and output?

 

[e.oelberg]

Are you using LL1517 both on input and output?

no 1540 and 1517  but I'm not happy with the result, I have a roll off of the highs. This is the next problem. But I really like this unit transformerless

nicholas

 

[e.oelberg]

Are you sure it's ground hum?  I had a similar problem because of voltage sag dropping the PSU out of regulation, causing a buzz/hum.  That would be consistent with you having to run both boards before it starts.  What are your toroid specs?

thanks very much... this was the hint. I replaced the 24 24 trafo with a 30 30 the hum/buzz is gone. It wasn't a ground loop the toroid was to stressed.

so I learned something, thank you very  much,  Nicholas

 

[haima]

Great! that makes sense.  8)

 

[briomusic]

I'm planning to stick to the original 6 positions (instead of 9) on the Recovery switch. I've been comparing the original EMI schematic to the TG1 build version and the resistors on the switch are similar in value in most positions on each schm. My question is regarding what to do with the positions I'll be leaving out.
On the TG1 build schematic the unused positions (10 & 11) on the 12 position Recovery switch run off to 2 resistors; R208 and R205. Should I do the same with the empty positions I will have after using 6 of the intended 9 positions? BTW, position 12 on the schematic is not connected to anything at all. Why is this? I would appreciate some help on what I should do with the 3 empty spots I'll be creating by going down to 6. Thanks.

you can limit the lorlin rotary switch to as many - or few - positions as you like by changing a little washer type thing from the front. you don't need to connect anything to the remaining, inactive positions and related pins. alternatively, you can connect everything if you later decide that you would like the additional options. in that case you just need to change the 'limiting-washer' back to 11.

 

[grantlack]

finally getting around to this one, had a quick question- in the 'bypass versions' documentation, when referring to R1-4 i'm assuming it's in reference to what's labeled as RIN1-4 on the bypass boards and not R1-4 on the mainboard?

now i have to track down the packet of bc177's i ordered off ebay and promptly misplaced f($#*@king two months ago  :

 

[pachi2007]

Motorola papers say the bc214 should be put opposite way as marked on the pcb. I´m I right? should I turn it or just go to sleep?
Thx people
Pachi

 

[haima]

There's actually numerous (3?) pinouts for the BC214... if you do a search in this thread and the 2254c build thread you'll find some discussions. I've used the BC214L in my 2254C - i just had to partially rotate them to get the pins in the right holes.

Best thing to do is to use your multimeter to check the pinout of the devices you have, and then place them in the holes accordingly. You might need to rotate or flip - or you might match the top screen print. Igor has kindly put marked "E", "B" & "C" so it's pretty easy.

 

[Hank Dussen]

OK back to my TG1.
Finally solved my transistor and power problems. Unit passes audio and compresses but I'm still struggling to get the satifying threshold levels and meter readings.
I tried 5K and 10K for the hold pot and different values for R115.
Compression only happens in the last quarter of the hold knob.
Meter swings only between +5 and +15. And not a lot.
This doesn't feel completely right.

What values do you guys use for the hold pot and R115 and at what position do you get unity level?
At what position do you get the meter to zero?

 

[Rob Flinn]

I would be interested to know what value resistors people are using on the hold rotary switch ?

I used the values on the original diagram with a wire link for R115.  but I'm thinking that R15 might be needed bacause with the switch fully clockwise the output has massive gain & is clipping wildly.  I assume that fully clockwise should be unity gain ????

 

[StudioSQ]

I just went through my working unit again and it turns out that the two channels are slightly out of phase, maybe 90deg. when i put it up on the console meter it goes from full +1 to centered at 0 when the unit is engaged. and ideas about this? edcor 10k/10k in/out no bypass board nos transistors and diodes.

 

[StudioSQ]

I just needed to calibrate it better, sorry guys

 

[Hank Dussen]

Just curious: what's there to calibrate except for the optional hold pot trimmer?