[BUILD] 1176LN Rev D DIY

[okgb]

But if U.A. is using them ????

I can look at doing a grp buy out of Canada if there is interest ,
would have to be prepaid .

regards Greg

 

[Vas]

I would be in for that!
best regards
bill

 

[Echo North]

I'd be in for 4.

Mike

 

[Bri]

I'd definitely be in for one.

--Brian

 

[maxwall]

I suppose I'd take a T-600 attenuator from either PEC or Precisionsales, makes little difference to me. But a group buy will be good in keeping the price reasonable. In the meantime, I'll build a 0-20db , 2db incremented rotary stepped attenuator like below or NYD's design to suppliment the immediate need, until I get my pinchers on the T600 real non-rotary t-attenuator.

Leeds radio supply has only one Mallory T600 3 deck left for $53 , so that source is now dry.

I'm having trouble reading pages 41-42 of the 1176 Manual found at

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/UREI-1176LNmanual.pdf

, are they even relavent to the build, I wonder ?

***

 

[Echo North]

I emailed Leeds yesterday as well! I decided not to pick up his last T600. I need two anyway.

I recall reading that some builders did not like their feel. Keith maybe?

Thinking about trying to make my own as well.

Mike

 

[emrr]

I bought a lot (30?) of the Leeds NOS Mallory (EDIT!! CLAROSTAT!!!) T's many years ago, and 3/4 of them were bad. Leeds refunded me, no problem. They have a riveted piece that locks the decks together that seems to have broken loose on most of them. The ones that work tend to be noisy when rotated, being wirewound. I wouldn't consider that type to be first choice.

Manley uses some variety in the Vari-Mu limiter; might be worth checking their source/price.

 

[maxwall]

Doug,

Thanks for the prosumer awareness alert on the mallory types.
will be steering clear of those in the future.

was the loose rivet causing contact issues due to the inceased play inside
the attenuator housings ?

 

[ruairioflaherty]

FYI I bought two of the Mallorys from Leeds the last time I was in New York. The NOS and the plastic bags inside were sealed. I haven't used them yet as I'm still slowly gathering the key parts for an authentic rev D but I can say that the feel is a little rough but not such that it would concern me. They are also a lot bulkier than the newer alternatives but that shouldn't concern us because of the neatness of Mnats pcb (good job!).

I'm hoping that these are a different batch to the ones Doug had trouble with, I bought 'em last July. I'd be in for 5 of the PEC or precision sales versions if anyone has the patience to organise a group buy. I'd gladly step up but my location rules it out.

I've got the O12s, Modutecs, 600 Ohm attenuators and pcbs for 2 builds - working on a local parts lists, getting excited now.

Cheers,
Ruairi

 

[nielsk]

The 3 deck units from State as used by Purple (they used the original version in early units, wound up having to change them all out as they went scratchy) work great, very smooth. Why would you want to use anything else?

 

[emrr]

[quote author="maxwall"]Doug,

Thanks for the prosumer awareness alert on the mallory types.
will be steering clear of those in the future.

was the loose rivet causing contact issues due to the inceased play inside
the attenuator housings ?[/quote]

The Clarostat decks were amputated from one another, or so loose that end travel caused circuit disconnect. The shaft does not go through all three decks. The riveted piece is the 'hand' holding two shafts together. EDIT: pics posted on the next page.

At the time, I attributed the deaths to poor storage; box of loose pots all crushing one another, possibly also dropped in shipping. At any rate, it's a part that will wear out in use, and wire-wound scratches when turned so you don't adjust in use.

 

[mitsos]

I'd also be in for 2 attenuators if this group buy happens...
It's the missing link for me, (as long as I can get my hands on o/t from Ed!)

Thanks Maxwall for posting the switch diagrams...

 

[Echo North]

Hi Maxwell,

Do you have a good source for 2-pole 12-pos (MBB) switches for home made t-pads? Lorlin doesn't seem to make 2-pole 12-pos and digi and mouser came up dry. There is this Grayhill...but it's a 2 pole 2 deck 6 position...which I assume is different then 2 pole 12 position. They also have a 1 pole 12 position 2 deck model.

Frankly I'm done with the T-pad attenuator search. If I can make a switch that will do the same thing that's fine with me!

For anyone who cares, I spoke with precisiosales this morning:
Bridged attenuator model 05-0007 600ohm
US$38.90
25 Min Order.

I WILL NOT BE MAKING THIS ORDER. This is just for those interested in starting a group buy.

-Mike

 

[dissonantstring]

mike,
mouser does have a 2 pole / 12 position rotary (MMB-shorting).
mouser #: 105-SR2921F-12S
it has two wafers and 1 pole / 12 positions per layer. i've used them before on my 1272 Hot Rod with greg's pcbs.

they are cheap and feel pretty good, the catch...they don't have any end stops. but in the LAB you know someone's figured this one out right? Thank you to NYDave in this thread
hope this helps!
-grant

 

[Echo North]

Oh that is perfect!

I missed that NYDave thread in my searches. I did see his thread on resistor values.

Thanks a ton Grant!

This is definitely the route I am going to take.

Mike

 

[maxwall]

Grant , Mike

the Alpha 105-SR2921F-12S , a DIY favorite.

I'm thinking of groupbuy on the Bridged attenuator model 05-0007 600ohm

Does anyone know if EdAnderson has this covered ?

 

[edanderson]

[quote author="maxwall"]Does anyone know if EdAnderson has this covered[/quote]

ooh ooh, i know.

no. i will not be buying any PEC attenuators.

ed

 

[maxwall]

Ed ,

what a laugh.. did'nt expect that reply.

Ok maybe I'll start the T attrenuator group buy ?

As you know, Were all anxious for your transformers now.

 

[edanderson]

[quote author="nielsk"]The 3 deck units from State as used by Purple (they used the original version in early units, wound up having to change them all out as they went scratchy) work great, very smooth. Why would you want to use anything else?[/quote]

this is not quite right. the original 2 deck attenuators from clarostat were fine, they worked forever and we even used old surplus NOS units. when they were discontinued, andrew started using the 3 deck modpot from state. years later, when we looked at the PEC 2 deck attenuators, we heard from some UA users that they went scratchy; the sample we had seemed okay at first.

anyway, the 3 deck attenuators from state are very likely to be considerably more expensive than the PEC 2 deck attenuators. but they do work well, which is why purple continues to use them.

ed

 

[maxwall]

Just send a quote request to state for quantity pricing for potential group order.