source for 3 parts for 3rd gen. 50W

[telentubes]

I'm looking for part numbers and sources for these last three parts for a 3rd generation ODS 50W, as drawn by Talbany. Any help would be appreciated.
Thanks.

1.) The proper relay which will be powered by the F-313X transformer.

2.) The 2n3823 687V for the FET board.

3.) 20AWG stranded, teflon covered core, RG58 or RG59, copper or silvered copper coax (or any other appropriate coax in lengths under 100'/1000'). The white stuff is cool.

I can't seem to track theses down.

I'll be using a Hammond P-T290EX for the PT, but haven't found the right OT yet.

Thanks everyone!!! Here's a pic of the not quite finished boards.

[martin manning]

For the TO-72 (metal can) FET, a 2N4416A will work fine, and they are in production and available from Mouser. 2N5078 looks to be even closer to the 2N3823 spec, American Micro Semiconductor has those for ~$6. Even listed on Amazon! Plan on tweaking the 1.6k bias resistor to get the FET circuit dialed in. Try Apex Jr for the wire...

[ToneMerc]

I'm looking for part numbers and sources for these last three parts for a 3rd generation ODS 50W, as drawn by Talbany. Any help would be appreciated.
Thanks.

1.) The proper relay which will be powered by the F-313X transformer.

Here's the actual exact original relay; Calrad 40-677: 12V DPDT, 250 ohm , 50mA coil. It's basically obtainium, it was made in small batches mainly for another Calrad product and Calrad stop selling the relay years ago. HAD most likely picked these up as surplus given the way loved using donar and surplus parts. If you just got to have a Calrad labled part, there's a Calrad alarm card board that has a Calrad 12V DPDT relay on it.

Otherwise, look for a sealed, blade plug 12V DPDT relay with similar specs and don't forget the appropriate chassis socket.

Also, the F313X was only found on the multi-voltage amps as it was setup for both 120 and 240 volts . If you are only going to wire it for 120V, use the F-13X, it's the same transformer with only a 120V primary. I've grabbed NIB, new old stock(era/markings correct) units from eBay for less than $5 in the past.

2. A 2N4416 or 2N4416A makes a great substitute.

3. Steve of Apex Jr should be able to help with the coax.

TM

[telentubes]

Thanks Martin! I've got the FET in on my "punch list" order from Mouser. 1 down, 2 to go. I'll call Apex, after the long weekend, to see what they have in stock.

[martin manning]

A couple of tips for getting the FET dialed:

To find the right bias (source) resistor, I clipped 18V (from two 9V batteries snapped together) to the top of the 10k drain resistor, and then used a pot to find a source resistance that resulted in 9V (half of the supply voltage) at the FET's drain (the other side of the 10k). Start high with the resistance, 10k maybe, and come down while watching the drain voltage come up.

The other thing you will likely need to do is increase the 8k2 leg of the 150k-8k2 voltage divider to get ~20V at the top of the 10k when it is powered by the amp's B+. The 8k2 will likely be more like 25-27k.

[telentubes]

ToneMerc,
I found this F-13X at Mouser. Is this the one I need?...
http://www.mouser.com/ProductDetail/Tri ... nBPw%3d%3d

I will try to track down the relay. Thanks for the lead.

[martin manning]

Mouser 655-KRPA-11DY-12 (12 VDC, 5A rated general purpose octal relay)... unless you really want the blade-type base and socket.

The F-13X transformer looks fine.

[ToneMerc]

ToneMerc,
I found this F-13X at Mouser. Is this the one I need?...
http://www.mouser.com/ProductDetail/Tri ... nBPw%3d%3d

I will try to track down the relay. Thanks for the lead.

Yes, that is the modern F-13X. If you want the look, find the older NOS units in the red/white Triad carton that have 115V, 60 C.P.S. printed on them.

Good luck in trying to find that Calrad relay. Now, I haven't looked for one in awhile, but one could turn up anywhere and anytime. When I was looking over year and a half ago, I found a VP at Calrad that was nice enough to look around to see if a unit was left around anywhere, no dice.

good luck

TM

[telentubes]

ToneMerc,
I'm fine with the modern F-13X.
Between your suggestions and Martins, I'll pick a relay.
Last up is the coax, which I'll score from Apex after the weekend.
And Martin, thanks for the FET fine tuning tips. They will come in handy (At first, I was on the fence about whether to include the FET ).

Thanks you guys!!!

[Matt J]

Great looking board build there Telentubes!

Martin, I'm definitely going to use your FET fine tuning tips for my own #102 build I'm currently working on.

Teletubes, I see that you marked the outer foil on your coupling caps. What method did you use to do that? I tried Gerald Weber's tinfoil method (I do not have an oscilloscope) and could not seem to get it to work.

- Matt J.

[Structo]

Keep in mind Apex Jr has a minimum order of $20-25.

[telentubes]

Tom... I need some pots as well, so $30 will be easy. You know how that goes. Harder to keep it under $100.

[telentubes]

MattJ,
I built this tester as described in this YouTube video...
http://www.youtube.com/watch?v=VP6ZIHXq6Yg

And here's one of several threads...
https://tubeamparchive.com/viewtopic.ph ... +direction

[Structo]

Yeah that works pretty slick, I built one as well.

Be sure to turn up the volume pretty high on the amp you connect it to and be sure to install a on-off switch that shorts out the tester when you don't have a cap on it to kill the noise.

[amplifiednation]

I made one of these testers last week. It went together in fifteen minutes and worked great. It is surprising that there really is such an audible difference to the outer foil blocking abilities.