New build questions

[brentm]

Just out of curiosity. How high do you guys stand off your preamp and power circuit boards from the chassis? It's tough to tell in pictures because everything looks so enlarged.

I have a backer board for both boards, so it'll be up just slightly higher than it is now. Right now I have a couple washers in the stand offs, so it's about 10mm off the chassis. Is this sufficient, or should it be up a little higher? I haven't run into the issues of fitting everything inside this box yet and am hoping to hear from some of the experienced folks on here.

Another question was on the output ohm selector switch. I think I'll just go with 3 output jacks for 4, 8, 16 ohms respectively instead of the rotary switch to select the output impedence. This will use the 2 speaker output chassis holes and the switch hole. Any potential issues with this?

Right now, I'm waiting for a couple orders and still have yet to purchase power/output trannies and and the choke. I guess I'm circling the drain on those... and basically staging all the hardware trying to get correct fitting screws/nuts/washers, etc. This CE Chassis is awesome! Those guys do amazing work!

[brentm]

Ah well the picture revealed something I hadn't noticed. I mounted the tube sockets on the wrong side!!

[ToneMerc]

Just out of curiosity. How high do you guys stand off your preamp and power circuit boards from the chassis?

I use round 6-32 alum standoffs; .625 for the power and .750 for the preamp board.

TM

[brentm]

Just out of curiosity. How high do you guys stand off your preamp and power circuit boards from the chassis?

I use round 6-32 alum standoffs; .625 for the power and .750 for the preamp board.

TM

Thanks ToneMerc! Looks like I should raise them up a bit then. Appreciate it!

[ToneMerc]

I've also done .500 and .625 as well. I like it slightly higher because I like to use .375 and .250 long button head or cap machine screws to secure both the standoff and the board. Use whatever works best for you.

TM

[Structo]

I think the nylon spacers I used were 1/2 inch.

[brentm]

Thanks guys! I got some spacers coming that are closer to half inch. Staying with metric since I started with Harwin spacers from Mouser and purchased a bunch of machine screws and paid way too much. I almost thought it'd be handy to put together a screw/bolt/washer pack for these amps. Seems like the only piece of hardware missing from the community suppliers. I do have some nylon locking nuts for the finished product, but am waiting to use them.

Next question relates to the power board. I tried to come closer to Dumble values while staying in the sprague line. I found some 220uf caps. They're -10 / +50 percent tolerance. They measure a little over their stated value on my multimeter but I would suspect at operating voltages may go up a higher (perhaps to the dumble 330uf). Should I use these or go with 2 100uf Sprague TVA-1620s... I could cut another board with a little more room to fit these bad boys on.... My other concern is it looks like these caps have been on the shelf a while. Judging by the date code... 1990. Thoughts??? Suggestions????

Thanks!

[ToneMerc]

Thanks guys! I got some spacers coming that are closer to half inch. Staying with metric since I started with Harwin spacers from Mouser and purchased a bunch of machine screws and paid way too much. I almost thought it'd be handy to put together a screw/bolt/washer pack for these amps. Seems like the only piece of hardware missing from the community suppliers. I do have some nylon locking nuts for the finished product, but am waiting to use them.

Next question relates to the power board. I tried to come closer to Dumble values while staying in the sprague line. I found some 220uf caps. They're -10 / +50 percent tolerance. They measure a little over their stated value on my multimeter but I would suspect at operating voltages may go up a higher (perhaps to the dumble 330uf). Should I use these or go with 2 100uf Sprague TVA-1620s... I could cut another board with a little more room to fit these bad boys on.... My other concern is it looks like these caps have been on the shelf a while. Judging by the date code... 1990. Thoughts??? Suggestions????

Thanks!

Personally, I would never use 20+ yr old caps at the B+1 location and if I did, they would at least be reformed first.

TM

[Structo]

I agree.

[brentm]

Yeah. 1990 doesn't seem like that long ago!

I found some 350uf 450vdc Tech Cap caps at my shop for 50 bucks a pop. Ugh. Ill do better online. But the caps were sexy sprague blue and screw terminal.

[brentm]

I think I'll just go with 220uf 300vdc F&T caps. Thanks guys!

[brentm]

Just an update.. I ended up going with some TVA1720 "Special Radials" on this..

Kind of a shot in the dark. I couldn't find the case dimensions for these caps but we'll see. Spendy little buggers, but I really wanted some Spragues and these seemed close to the mark.

http://www.mouser.com/Search/ProductDet ... 75-TVA1720

I also just ordered the transformers from Triode Store... Hopefully by this weekend it'll be time to get to work!

[ToneMerc]

Kind of a shot in the dark. I couldn't find the case dimensions for these caps but we'll see.

1720; if they are the ones I remember seeing, I think you will be in for a surprise.

good luck

TM

[brentm]

Are they fatties?

[brentm]

Also, I have no doubt the 39D caps are expired. But I received a response from Sprague on shelf life calculation.

Here was their response.

thank you for asking,

39D is an 85°C product and the shelf life for 85°C products is 1.000h.

Yes, 9024H is the date code,

Year 1990 and week 24!

So, is 1.000h a "henry" unit? And if so, how wouuld you calculate shelf life based on that. I know some caps have 6.000h storage life in them.