TLP Transformer connections

T-Bone · « **on:** 28 Nov 2003, 03:20 pm »

Hi,
Would someone care to refresh my memory on the 6v secondary connection? I believe the two filament leads terminate at the 0v and 6v tags. Also, would anyone like to recommend an inexpensive pot? Thanks, Brad

AKSA · « **Reply #1 on:** 28 Nov 2003, 07:59 pm »

Hi Brad,

Yes, the 0 and 6V tags are the filament; I underrun it a little to prolong filament life, and because the mains in most countries is usually higher than nominal.

A good pot? Try the ALPS blue (RK27); not too expensive, but up with the good ones and nice value for money.

Cheers,

Hugh

T-Bone · « **Reply #2 on:** 29 Nov 2003, 03:47 am »

Thanks Hugh. I'm only seeing 4.85V at the 6V & 0V tags @119V. At the 150V & 0V tags I had 38.80V. At the B+ I was reading infinity. Transformer was hot to the touch as were the caps. As soon as I seen the infinite reading I hit the switch on the variac. The filament was barely glowing. I wanted get a few more readings but under the circumstances I didn't think that would be wise. Brad

T-Bone · « **Reply #3 on:** 29 Nov 2003, 04:58 am »

Disregard the previous post. Bad connection on the primary and new batteries in the meter.
119V @mains
5.98V @6V tags
172V @ 150 tags
182V DC side of bridge no load
1.6V across R8
R7 Infinite with respect to ground Per Step 14 of your text
It appears I have made error(s) on the board

Thanks! Brad

T-Bone · « **Reply #4 on:** 29 Nov 2003, 02:15 pm »

Re-soldered all connections and checked component placement on the board. OK
R7 R7 Both now 218V (yikes!) with respect to ground Per Step 14 of your text
B+ 223V to ground
R8 still 1.6V
R4 A/B 32V
Brad

AKSA · « **Reply #5 on:** 30 Nov 2003, 01:01 am »

Brad,

1.6V across R8 is too low, and the voltage across R4A/B at 32V confirms this. This last should be around 45 volts, and indicates the tubes are not correctly biased up.

Check R3, R8, R9 are the correct values as per instructions, and the voltage at R7 is nominally 140. This is the object of the exercise; that R7 has 140V wrt ground. Make sure the rectifier is correctly wired at the transformers; crucial of course.

Failing this, my suggestion would be to grab a digital camera and start sending photos to my email address; I will download on return from South Australia in a couple of days and give them my immediate attention, but right now I have a family trip scheduled.

From the photos I should be able to pick up any problems, but will need two top and two bottom photos of the whole pcb.

Hope this is helpful,

Cheers,

Hugh

T-Bone · « **Reply #6 on:** 30 Nov 2003, 06:53 am »

Please stay focused while behind the wheel and have a safe trip.

I'll re-check everything while you are away and as always I appreciate your help. Brad

T-Bone · « **Reply #7 on:** 15 Dec 2003, 11:12 pm »

Hi Hugh,

Hope you had a nice trip.

I desoldered one end of all resistors. It appears that I swapped R3 with R5.

Question is looking at the color coding I come up with 487R not 487K and 464k not 464R as your text indicates. I have some new 470R resistors but I'm stuck with the 464k. Will the difference in values create a problem?

Thanks,
Brad

AKSA · « **Reply #8 on:** 16 Dec 2003, 03:51 am »

Quote from: T-Bone

I desoldered one end of all resistors. It appears that I swapped R3 with R5. Question is looking at the color coding I come up with 487R not 487K and 464k not 464R as your text indicates. I have some new 470R resistors but I'm stuck with the 464k. Will the difference in values create a problem?

Hi Brad,

R3 can be 464K, but any resistor from 150K upwards is just fine here.
R5 is a ground reference tiedown; it's value is not important and anything from 100K to 1M is fine. It's purpose is to prevent a huge thump when you connect the TLP output to a power amp, nothing more.

Neither of these resistors is important to sonics; although lower is better for R3.

Hope this helps,

Cheers,

Hugh

T-Bone · « **Reply #9 on:** 16 Dec 2003, 08:30 am »

Hi Hugh,

Well we are getting close.
12.4V across R8
145V at R7 wrt
222V at B+
R4 A/B .405mv ???????

I'll send photos when I get up. I must have over looked something.

Thanks for your time!
Brad

AKSA · « **Reply #10 on:** 16 Dec 2003, 11:54 am »

Hi Brad,

Measure across R4A; I'm pretty sure it's drawing current as it should, and you are probably measuring from left of R4A to right of R4A'.

With the correct B+ the tube can only be drawing the proper current.

Cheers,

Hugh

T-Bone · « **Reply #11 on:** 16 Dec 2003, 11:48 pm »

Hi Hugh,

With one probe far right and the other far left touching both resistors on either end I observed 2V.

Thanks,
Brad

AKSA · « **Reply #12 on:** 16 Dec 2003, 11:58 pm »

Brad,

This tells me that you have a 2V differential between the two cathodes, one for each channel. This is a good sign, because it certainly indicates current is flowing and arguably there should now be current flowing through R4A and R4B.

Maybe you should check you DMM battery; if flat, it will give false readings.

If the battery checks out OK, then again measure voltage:

1. Across R4A.
2. Across R4B (should be the same as R4A, and around 50V)
3. Across R4A'.
4. Across R4B' (same as above).

I am pretty sure there is current flowing through these resistors. The question is how much!

Cheers,

Hugh

T-Bone · « **Reply #13 on:** 17 Dec 2003, 12:58 am »

Hi Hugh,

1. Across R4A. 50V
2. Across R4B 50V
3. Across R4A'. 52V
4. Across R4B' 52V

Too high??? (Used two different meters that are 0.3V of each other.)

Thanks,
Brad

AKSA · « **Reply #14 on:** 17 Dec 2003, 01:21 am »

No, Brad,

That's fine. Should work very well now; all is AOK!!

Cheers,

Hugh

T-Bone · « **Reply #15 on:** 17 Dec 2003, 01:41 am »

Hi Hugh,

OUTSTANDING!!!

Thank you 'Sir for your valuable guidance. I'll post a photo when it's finished.

Brad