Western Electric 6BP Audiometer transform to 95A Amplifier Part 2

After I published the first part in 2 months ago about planning to make 95A amplifier. 

https://mellowgroovy.blogspot.com/2022/10/western-electric-6BP-95A-part1.html

Now I finish these mono-block amplifiers with some modifications from original schematic.

1) Using main power transformer instead of connect directly to power outlet

2) Using 80 full-wave rectifier tube instead of parallel 25Z5 tubes

3) Replace 221B with 221G choke (higher inductance)

4) Add WE313CC as voltage regulator & bleeding tube

5) Add LC filter to each screen grid for make lower noise voltage

6) Change some resistor & capacitor values based on real characteristic tube's curve

Expand some holes to put Neutrik connector both AC inlet (powerCON) and XLR input.

Almost US made components except transformers & choke from P&C Japan.

All 43 tubes are Raytheon 4 pillar (engraved base), 80 tube from Visseaux (France).

Top view

Close-up

Techlab PK-322 600 ohm attenuator

Raytheon 4 pillar

Visseaux 80 tube

Bottom view

Speaker terminals

Ready to use

Neutrik powerCON AC Inlet

Neutrik XLR input connector

Original Schematic of WE95A amplifier

Schematic of modified WE95A amplifier

It's sound very good especially instrumental. Transparency & good tonal balance.

Maybe need more burn-in time to get it's real sound.

Finally I finish this project and post to this blog within 2022.

Happy new year to everybody!

Cheers!!!

Western Electric 6BP Audiometer transform to 95A Amplifier Part 1

I've got these audiometers from yahoo auction couple months ago.

All tubes and transformers already gone. Only chassis and panel components left.

But layout, tubes and transformer enclosures made me think about Western Electric 95A!

Western Electric 95A amplifier & TA-4189 speaker are part of TA-7388 cabinet.

95A using single stage push pull 43 tube and 2 of 25Z5 rectifier tube.

No power transformer, can supply directly with 105 - 125 VAC.

Transformer needed are 282B, 174A and 221B filter choke.

So I think I can transform these 6BP audiometer to mono-block 95A amplifier

with adding full power supply section into same chassis.

Lovely cabinet with slot for collect cables!

Either position could be use as volume control.

Western Electric 6BP with full components. (pic from internet)

Something left ...

This Daven pot should be use as volume control but it has 5dB per step :( 

Heavy air capacitor!

Something inside left ...

After remove all of components & wires.

Original 95A amplifier. (pic from internet)

So I've order P&C (WE core) transformers to do this project. ;)

Let's see what will happen next ...

Studer D730 CD Player (Problem & Solution)

I've got this famous CD player from my friend with malfunction condition.

The problem is when power on the player, sometime it can run normally but will stop itself later

or cannot run since power on. Both situations indicate same word "Control Out" on display.

After search many information on internet, I've found this is common problem that many person had.

First they've recommended to replace Ni-MH battery that always leak after time has passed.

But after replacing battery, "Control Out" still appear on display.

Leaking Ni-MH battery cause hydrochloric acid so need to clean up nearby components.

No conclusion for real problem until I've found "Service Note 99-04" from Studer.

https://www.reeltoreel.nl/studer/Public/Products/CD/D730-D731-D739/Technical_Info/D730_D731_SN99-11.pdf

This service note mention about the defect of LM317T regulator IC and cause over-voltage to HEF4750

which is frequency synthesizer IC. So it can be damaged and effect the deviation of nominal speed.

I already read this note and follow the procedure to remove existing HEF4750 

then replace with 28 pins IC socket and use new HEF4750. I've found a good looking HEF4750

with ceramic body and gold pins on ebay, seem worth to try for me.

Compare existing HEF4750 and the new one with ceramic body & gold pins.

Using socket instead of directly solder to IC's pins.

But I thought capacitors in main power supply section on mainboard should be upgrade 

in same time too. So I select to using Nichicon KG (Gold Tune) amd KS (High Sound)

depends on original dimensions because of limit space to use all KG in this area.

Components that have been removed.

After replaced with higher quality capacitors.

I also found this great forum here

https://www.audiovintage.fr/leforum/viewtopic.php?t=45201

that use smart idea to fix LM317T heat problem with move this IC to main heatsink

using connecter and wiring. So I've made with new LM317T like this 

and I thought this is the good way to follow.

Existing LM317T located in limit space between large capacitors and connecter.

After remove LM317T to main heatsink with connecter & wiring.

Add heatsinks to LM317T & LM337T near TDA1547 too.

After replace all components that I've mention, then I turn on power switch.

Everything work normally a long the week without any issue.

Seem this "Service Note 99-04" is the good guide if anyone had this same problem.

The sound of Studer D730 with TDA1547 "DAC7" is natural, not warm like TDA1541

but compromise with many kind of music. Will try external clock and external DAC later.

Cheers!!!