Vactrol alternate numbering

[armdnrdy]

I came across a few vactrols that I forgot I sourced in a lot with other items.

I have four Vactec Vactrols that are marked 21L554.
I recognized the "21L" designation from Mesa Boogie and MXR Phase 100 part lists so....I did a bit of legwork.

I found that VTL5C3/2  = 21L312
and VTL5C1 = 21L883

I cannot find the 21L designation for any other model.

Is anyone privy to the alternate factory numbering system?

[digi2t]

Funny. Peavey lists a 21L565 in the Encore 65, to which I've read that a VTL5C3/2 can replace.

The other place I've found Vactecs was in my Acoustic 160 (or G100T). They were used for the channel switching, although they used the "VTL" prefix. I have the datasheet for the incandesant and neon types, which also lists the old and new numbers, none start with "21L...".

You might get lucky if you look for old EG&G datasheets, the 21L numbers might be generic numbers, as mentioned on another forum.

[armdnrdy]

Thanks for the reply Dino!

It gave me another path with a few more numbers to search. I came up empty though. I'm working up a quick connect, LED/LDR test bed that's adjustable for different size devices...which can also be used for vactrols. I'll plop these 21L554 in there and compare the resistances with other vactrols that I have.

I had already scoured the net looking for data sheets other than what I have on file. I also looked at the incandescent and neon data sheet for reference.
I actually scored enough VTL9A10-2 incandescent dual vactrols for a go at a phaser with a slightly different touch. That one will be somewhere down the road.

[digi2t]

 

Quite the gold mine you've got there Larry!! Geez Louise, I tried sourcing some of those incandescent vactrols for my Acoustic, but they are unobtainium. I ended up retrofitting my G100T with VTL5C1's on a daughterboard instead, which worked perfectly.

As for the monoblocks with the 21L numbers, like you said, you'll have to test them and chart the results to cross-reference to the VTL numbers.

EDIT: Just had an idea. The Excelitas plant is just down the road from me. They're the present owners of the VTL vactrol production, so I've sent them a technical request.

Hello,
I have a question regarding Vactrols. I know that the products have changed hands quite a few times over the years, but I was wondering if you folks still had information in regards to the original EG&G nomenclature that was used for the VTL series of vactrols. I've recently come across some new old stock vactrols sporting the "VACTEC" name (was an EG&G division I believe), with the following part numbers on the reverse side; 21L554, 21L312, 21L883, 21L565. Would it be possible for you to provide cross-referencing for these vactrols, and any other numbers that may reference available VTL type vactrols?
Thank you,
Dino

Let's see what they can come up with.

[armdnrdy]

Good Idea! Thanks Dino!

Indeed...Excelitas is the last in line with the VTL series but...these items have been out of production since 2015.

Hopefully Excelitas will reply with some further info on them.   

[digi2t]

No go on the Excelitas reach out. Their rep stated the same thing, and said that they didn't have any EG&G info.

I did see that EG&G had an optoelectronic data book out at one time. I've looked, but I can't seem to find a downloadable version.

[armdnrdy]

Dino,

Thanks for trying!

I tested some VTL5C3s today for a different reason...and thought...let me throw one of the 21L554s in the same test circuit to see the difference.

Well....the Vactrol in question is definitely not a VTL5C3! The 21L554 has a much lower "on" resistance.

I'll have to run more tests with different vactrols...or...feed the 21L554 an exact current as listed in the data sheet...and see which model these are closest to.

[armdnrdy]

For what it's worth...

I found some additional info on another Vactec vactrol.

Maybe this will help someone down the line.

The alternate "21L" number for a VTL5C4 is 21L884.

[digi2t]

That's what I've read on a French website on Mesa Boogie troubleshooting.

884 = C4
883 = C1