Manley Vari Mu T-Bar reverse-mod to 6386?

[distorter]

Does anyone know how to reverse mod a T-Bar Variable Mu to 6386? I have a Manley Vari Mu Version 4 and a T-bar in it as shown on the pics.

I talked to Manley support, they want me to send the unit back to factory and ask $300-$500 for it.

I believe this is going to be a simple mod. Anyone has any experience on it?

Thanks in advance!

 

[mkiijam]

Yes, just have them send you the mod procedure and then work backwards.

 

[rackmonkey]

Can i ask why?

 

[distorter]

Yes, just have them send you the mod procedure and then work backwards.

I wish. But they insist that this is a complicated mod which only their senior technician can perform…

 

[distorter]

Can i ask why?

Because everyone says 6386 is better than T-Bar. I believe so based on my own experience. Original 6386 is ALWAYS the best.

 

[gyraf]

..but 6386 is a remote-cutoff tube, the 5670 (and its mod variants) is sharp-cutoff. Can you just use them interchangeably?

If going this route, please note that the new-production JJ 6386 are absolutely horrible quality - be that either because of bad production or them selling off unmatchables to private/small customers

/Jakob E.

 

[distorter]

Can i ask why?

Because everyone says 6386 is better than T-Bar. I believe so based on my own experience. Original 6386 ALWAYS the best.

..but 6386 is a remote-cutoff tube, the 5670 (and its mod variants) is sharp-cutoff. Can you just use them interchangeably?

If going this route, please note that the new-production JJ 6386 are absolutely horrible quality - be that either because of bad production or them selling off unmatchables to private/small customers

/Jakob E.

I took off the t-bar and tried 6386 on it but no luck. I think minor modifications are needed on the circuit. Maybe a mod from 5670 to 6386?
Yes, JJ’s 6386 is terrible. I’d use a NOS ge 5-star 6386.

 

[emrr]

The additional parts on the T bar will be the value extensions to turn 5670 into 6386.

 

[gyraf]

..so external components turns a sharp-cutoff tube into a remote cutoff one? How..?

 

[distorter]

..so external components turns a sharp-cutoff tube into a remote cutoff one? How..?

Is this not possible? emrr’s advise sounds feasible, but I am not sure.

 

[Jase_Sanderson]

I wish. But they insist that this is a complicated mod which only their senior technician can perform…

Getting the same response from them but i'm wanting a t-bar. Would love it if someone could sketch out a schematic of how the connections with the resistor values are... So i could make one

 

[distorter]

Getting the same response from them but i'm wanting a t-bar. Would love it if someone could sketch out a schematic of how the connections with the resistor values are... So i could make one

You can refer to the picture I post. You can also find some informations on T-Bar in the forum. Good luck on your conversion. Let me know if the mod works. Manley’s service is really bad, also their products in recent years. Seems to me they are desperately squeezing costs and ripping off moneys with the products with the same looks but worse qualities.

 

[emrr]

The T bar is to make a 6386 out of the two 7 pin tubes, replacing the 5670. Everyone uses the pairs and the 6386 interchangeably. Logic follows that…..

 

[scott2000]

More clues maybe?

https://groupdiy.com/threads/drip-dual-sta-build-dual-6ba6-option.77296/
https://groupdiy.com/threads/sta-level-6386-to-6ba6-t-bar-wiring.78033/
Could trace that board out pretty quick?

 

[martthie_08]

1) Replace 3k57 resistors connected to pins 4 & 6 of 5670 socket with 6k8 1W.
2) Replace 1k resistors connected to pins 2 and 8 with 511 ohms.
3) Replace 10k “balance” trimpot with 500 ohm trimpot.
4) Remove 200 ohm resistor between pins 2 and 8.
5) Replace 33k 1W resistor between wiper of “GR cal” trimpot and the junction of the meter with 22K 1W (resistor is located near the rear corner of the pcb next to the GR cal trimpot).
6) Repeat procedure for the other channel; re-calibrate as outlined in the owner’s manual.

This info was given to me many years ago, I have no idea whether it is accurate!

Please note that this mod is for a non T-Bar Vari-Mu.

 

[distorter]

1) Replace 3k57 resistors connected to pins 4 & 6 of 5670 socket with 6k8 1W.
2) Replace 1k resistors connected to pins 2 and 8 with 511 ohms.
3) Replace 10k “balance” trimpot with 500 ohm trimpot.
4) Remove 200 ohm resistor between pins 2 and 8.
5) Replace 33k 1W resistor between wiper of “GR cal” trimpot and the junction of the meter with 22K 1W (resistor is located near the rear corner of the pcb next to the GR cal trimpot).
6) Repeat procedure for the other channel; re-calibrate as outlined in the owner’s manual.

This info was given to me many years ago, I have no idea whether it is accurate!

Please note that this mod is for a non T-Bar Vari-Mu.

Thank you!

 

[rackmonkey]

Quote from distorter:

Because everyone says 6386 is better than T-Bar. I believe so based on my own experience. Original 6386 is ALWAYS the best.

The reason I ask is practical. Triode strapped 6BA6 is for all intents equivalent to half of a 6386. So I'm just not sure what you think you'll get from switching to 6386 as I can't tell any difference between matched 6BA6 and 6386 in my Sta-Level and my modified CBS Audimax IIrz. I haven't been impressed with the modern JJ 6386. And NOS have gotten nearly impossible to find and stupid expensive. I can buy boxes of 5749 (mil-spec 6BA6), and match them with my simple eBay curve tracer better than you'll typically get in a single bottle with the 6386. So I've just gotten away from 6386 (and won't be building/buying any other 6386 based compressors). Hence my question.

 

[emrr]

1) Replace 3k57 resistors connected to pins 4 & 6 of 5670 socket with 6k8 1W.
2) Replace 1k resistors connected to pins 2 and 8 with 511 ohms.
3) Replace 10k “balance” trimpot with 500 ohm trimpot.
4) Remove 200 ohm resistor between pins 2 and 8.
5) Replace 33k 1W resistor between wiper of “GR cal” trimpot and the junction of the meter with 22K 1W (resistor is located near the rear corner of the pcb next to the GR cal trimpot).
6) Repeat procedure for the other channel; re-calibrate as outlined in the owner’s manual.

This info was given to me many years ago, I have no idea whether it is accurate!

Please note that this mod is for a non T-Bar Vari-Mu.

That looks correct. So ditch the T-Bar, change those values, and you should be there. The T-bar will be doing the changing for you, for the pair of tubes.