DIY JE-990 DOA

[hejsan]

Ok thanks, so 2 questions left:

mnats: In your 990 pdf you list C4 and C5 as 1uF, but I'm guessing that's supposed to be 0.1uF, right?

The 62pF cap, how important is it to have it excactly 62? Would 56pF or 68pF do?
I can see from the photo of your 990 that it has a through hole cap where the 62pF should be, could you possibly source it? I have pretty shaky hands and am afraid of smd..

Has anyone else found 62pF in non-SMD form?

Thanks,
hejsan

 

[hejsan]

Anyone?

 

[AnalogPackrat]

Hejsan,

Digikey in the US carries several NP0/C0G thru-hole caps in 62pF. You should be able to find a European outlet that carries something similar. That said, I imagine you could sub 56pF or 68pF if you have it. I'm not sure how critical the exact value is, but most of these caps are +/-5% anyway which means 62pF could be 59-65pF. Go through a set of 56pF and select the ones that stray toward the high end or use 68pF that are toward the low end of the tolerance band.

A P

 

[evm1024]

Lots of us are sourcing parts for out 990 boards. Perhaps it could save us some time to post a list of Digikey (etc) catalog numbers for others use.

I have not had the time to look them up (too much real work getting inthe way) and it would be a great help.


Regards, Ethan

 

[hejsan]

I have looked at digikey and don't see any thru-hole 62pF.
Could you/someone point me towards it?

Thanks a lot,
hejsan

 

[hejsan]

What do you people think about this Mouser part number:
5982-15-500V62

It's a "Mica Metal Clad RF Capacitors 500V 62PF MICA CAP"

it is 11.4mm long.

and costs 0.45 if you buy 50pcs and 0.36 if you buy 100pcs.

What is the purpose of this cap in the circuit anyway? is it passing audio?

Thank,
hejsan

 

[clintrubber]

What is the purpose of this cap in the circuit anyway? is it passing audio?

The stuff in the emitter of Q6 is 'in the signal path' for stability, it tailors the transfer function at high frequencies (above 3MHz).
If you want it all, check the Jensen-paper, section 3.

Speaking of tolerances, I've added some measurement data of the '20uH' inductor to this thread. It's on page 3, scroll down a bit to the blue-ish table.

Regards,

Peter

 

[hejsan]

Thanks.

But do you people think that this mica capacitor I found (see post above) would work?

Thanks,
hejsan

 

[dissonantstring]

hi all,
i just got some 30g. mag wire from my friend AnalogPackrat for the inductors and also some good info on how to thermal couple the two PN4250 pair on the JE-990. Thanks AP!
when looking at my mostly stuffed 990 board, i noticed that the inductor core would be touching the can of the LM394 when mounted. i also noticed that at least one of the inductors in mnats picture (on the first page of this thread) is touching the can also. is this bad? is there some consequence to this?
thanks.
-grant

 

[clintrubber]

[quote author="dissonantstring"]hi all,
i just got some 30g. mag wire from my friend AnalogPackrat for the inductors and also some good info on how to thermal couple the two PN4250 pair on the JE-990. Thanks AP![/quote]
Please share !

when looking at my mostly stuffed 990 board, i noticed that the inductor core would be touching the can of the LM394 when mounted. i also noticed that at least one of the inductors in mnats picture (on the first page of this thread) is touching the can also. is this bad? is there some consequence to this?
thanks.
-grant

The core is very highOhmic so I can't imagine a problem there.
But just in case, can you prevent it touching the case if you keep the coilwires a bit longer ?

Bye,

Peter

 

[dissonantstring]

[quote author="clintrubber"]
Please share !
[/quote]

oops! sorry peter. just put some thermal compound between the two transistor faces, couple the two and then put a large enough heatshrink tubing to fit around both and shrink tubing with heat. :grin:

[quote author="clintrubber"]
The core is very highOhmic so I can't imagine a problem there.
But just in case, can you prevent it touching the case if you keep the coilwires a bit longer ?
[/quote]

thanks for sharing that info peter! and i'll try to extend the leads, but i'm not sure if the 30g. will offer enough support to keep the inductor in the upright position. worth a try though.

regards,
grant

 

[dissonantstring]

BUMPITY, BUMP, BUMP!

hejsan asked this question, but never got a response.
i'm wondering the same thing. i ordered the 1uF caps because that was what was specified in the BOM of the JE-990 document mnats put together, but it seems that mnats also specifies 0.1uF in the reply below:

[quote author="hejsan"]
mnats: In your 990 pdf you list C4 and C5 as 1uF, but I'm guessing that's supposed to be 0.1uF, right?

[quote author="mnats"]

mnats..what caps are you using?

NP0 Ceramics for the small values and monolythics for the 0.1uFs.[/quote]

thanks,
hejsan[/quote]

it seems that it is supposed to be 0.1uF for C4 and C5 (as in the original schematic). can someone confirm this?
BTW, a big thank you to mnats for doing all the research and board layout!

kind regards,
grant

 

[clintrubber]

[quote author="dissonantstring"][quote author="clintrubber"]
Please share !
[/quote]

oops! sorry peter. just put some thermal compound between the two transistor faces, couple the two and then put a large enough heatshrink tubing to fit around both and shrink tubing with heat. :grin: [/quote]
Thanks for adding, the pic showed already something but since you mentioned you got some info I figured why not adding it here to make this thread more complete

[quote author="clintrubber"]
The core is very highOhmic so I can't imagine a problem there.
But just in case, can you prevent it touching the case if you keep the coilwires a bit longer ?

thanks for sharing that info peter! and i'll try to extend the leads, but i'm not sure if the 30g. will offer enough support to keep the inductor in the upright position. worth a try though.

regards,
grant[/quote]
You can try your cores yourself - all I did was check with a DMM set for Ohms, put the pins on the core some 5mm apart and measured. Note I was using another core - believed to be identical, but not the ones from the Ptownkid-kits (Ptownkit-kids ? :wink: ) IIRIC I got more than e few hundreds of kOhms.
Also briefly checked where the '394-can is connected to, but couldn't find anything in the datasheet.
But keeping them separated always better. How about supporting the coil with some blob of non-conductive stickysticky ?

Bye,

Peter

 

[hejsan]

Rebumpedy bumpabump..bump...
[quote author="hejsan"]What do you people think about this Mouser part number:
5982-15-500V62

It's a "Mica Metal Clad RF Capacitors 500V 62PF MICA CAP"

it is 11.4mm long.

and costs 0.45 if you buy 50pcs and 0.36 if you buy 100pcs.
[/quote]

Is there any reason to believe that this mica cap would perform worse than a np0 ceramic?

thanks,
hejsan

 

[imo]

I missed out on Ptowns parts kits. I have an order form for the dual transistor MAT02FH from Digikey, but the transistors are running 8.50 a piece and are not available until next year. DOes anyone have a source in the US for a more reasonably priced unit? The only other source i can find for the small amount i would use is Digikey as well, for the LM394ch which wouldn't handle the 24v supply.
Ian

 

[hejsan]

[quote author="imo"]..DOes anyone have a source in the US for a more reasonably priced unit?...[/quote]
At export.farnell.com:
http://export.farnell.com/jsp/home/...ome/exportHome.jsp.112_A&_DAV=en_EX_DIRECTEXP
They are available, but they will be shipped from the UK I believe. Be sure to pick lm394h (the best one) in non-RoHS compliant form. It is much cheaper than the lead-free version for some reason.

If you only need a couple, I'd just order samples from NATIONAL SEMICONDUCTOR.

Good luck,
hejsan

 

[imo]

Thanks for the tip. The export puts them pretty pricey here in the US. I'll contact National and see how many demos i can get
Ian

 

[Nele]

Also starting to build these and had the same questions as hesjan. I looked at John Hardy's 990-pdf, available here, and c4 and c5 are 0.1uF.
I think you can use just standard ceramic or polyester caps, as long as they fit the board, but John suggests ceramic X7R-types.

Anyone had any luck in finding the 62pF and 91pF COG/NPO-caps? Can't find 'm anywhere. (Farnell, Conrad, Reichelt don't have them)

Greetz,
Corneel

 

[clintrubber]

[quote author="Nele"]and c4 and c5 are 0.1uF.
I think you can use just standard ceramic or polyester caps, as long as they fit the board, but John suggests ceramic X7R-types.
[/quote]
I expect the usual suspects (multilayer caps, those yellow-earth-coloured small caps) will do fine here as well.
I mean, if we had been using an integrated opamp we'd been using the 0.1uF value and not unlikely those multilayers. Now for the '990 the local decoupling happens to be inside the DOA-box but that doesn't really change the situation.
And IIRIC multilayers are especially suited for decoupling.

 

[radiance]

[quote author="Nele"]

Anyone had any luck in finding the 62pF and 91pF COG/NPO-caps? Can't find 'm anywhere. (Farnell, Conrad, Reichelt don't have them)

Greetz,
Corneel[/quote]

Any news on these yet? I can't even find them in SMD form.
For the record...I looked @ RS, Conrad, Farnell, Elfa, Rotor Amsterdam, Stuut & Bruin, and some.... :sad:
Maybe a overseas group buy? I need at least 30 of each...