MP-1 Tube board caps

[shredbaron]

Hey folks,

In trying to troubleshoot my MP-1 (reversed dist/clean channels), I re-awakened my MP-1 obsession and desire to fiddle around with my soldering iron.

I spent today poring over schematics, websites, my MP-1's innards, making a list of components to replace to "refurb" my unit - replacing *all* the electrolytics, replacing audio path resistors with metal film, upgrading opamps, etc.

I'm having an issue finding appropriate coupling caps for C3, C9 and C10 (6800 pf, 200V) and C5 (1500 pf, 200V) - these are the blue mylar caps on the tube board, my C5 looks like a bigger version of C3 in the attached pic, not the white box C5 in the pic) - most of what I can find aren't dimensional matches or don't look the same.

I was looking at Orange Drops, they seem kind of big - but if I bend the leads, could I make them work? Doesn't matter if voltage is over spec, right?

http://ca.mouser.com/ProductDetail/Cornell-Dubilier-CDE/715P15256JD3/?qs=sGAEpiMZZMv1cc3ydrPrF%2fXaoGEw890Jf9aa6k7kk6w%3d

I also found these, but they aren't stocked...would this type of cap be even better?

http://ca.mouser.com/ProductDetail/KEMET/MMK5682J400J01L165TA18/?qs=sGAEpiMZZMv1cc3ydrPrF17gIuUB4mH1Os0WXxYko90%3d

I'd like to replace these 30 yr old components with the best available at a reasonable price, and since I'm placing a rather large order I figure I may as well get everything at once.

Generally speaking, if the capacitance is the right value and the voltage rating is at/above original spec, as long as the leads fit it should be fine (assuming it's the right type, of course - I wouldn't put ceramics in an audio circuit for example).

thanks in advance (and yes I'm learning by doing...any recommendations for a good electronics starter book for theory/concepts?)

George

[MarshallJMP]

You can use orange drops, the 400V are great but they are never in stock with mouser but the 600V work also.Problem is they don't fit next to each other (C9 and C10) so what you can do is stack them or solder one on the back.

http://www2.mouser.com/ProductDetail/Cornell-Dubilier-CDE/715P68256JD3/?qs=sGAEpiMZZMukHu%252bjC5l7YRGoyt%252b%252b9b9gBVk3BQbaSmA%3d

As for C5 I use these http://www2.mouser.com/ProductDetail/Cornell-Dubilier-CDE/150223J630DB/?qs=sGAEpiMZZMv1cc3ydrPrF9O2k7r3G2yZoaXPpo1NEhE%3d

These are 0.022uF.

[shredbaron]

Thanks, MJMP. I feel like I should be paying you for all this great advice.

Much appreciated - have most of my stuff ready to order, just gotta find that 2KS364/363 FET on eBay from a reputable seller.

Can't wait to hear it once I have it back together (assuming I don't botch something, that's a lot of desoldering/resoldering :) )

Any point in replacing C15/C14? Those are tantalums, apparently they don't degrade? Thoughts?

George

[MarshallJMP]

No problem, glad I can help out!!!  But if you want you always do a small donation to the depot. ;D

No leave C14/15 and BTW these are not tantalums but film caps. If they were tantalums I would have advised to change them  ;)

[shredbaron]

No problem, glad I can help out!!!  But if you want you always do a small donation to the depot. ;D

No leave C14/15 and BTW these are not tantalums but film caps. If they were tantalums I would have advised to change them  ;)

Donation made (I never noticed the Paypal donate button before LOL!) but I just sent some money to Dante :)

MJMP thanks again for responding. I actually realized this AM they were film, decided to put new replacements on my parts list. Also went with military spec metal film resistors.

Parts order is up to $102 CDN (actually $110 including the 2SK364 I ordered from eBay).

Only thing I have left is op-amps. Can't buy 2604s in quantities less than 150 from Mouser. Already have an OP2604 in U4, LF412 in U9 on the mainboard.

If I may ask:

1) I have socketed TL072s in U11 and U15. Any recommendations for something better?
2) U8 and U18 on the mainboard and U9 on the output board (effects loop) are 4559N - any upgrade suggestions?
3) U10 on output board is NE5532N (but I don't use the headphone out) and so is U12 on the mainboard. Any obvious upgrade to be made?

Sorry for all the questions, figure I may as well do everything at once.

[MarshallJMP]

The depot thanks you 

Metal film will help keeping the noise down a bit.

Yeah the OPA2604 is harder to find since these are no longer made in PDIP housings.I did once replace all the opamp with 2604's and that was too much for me, sounded too hifi.For me I only change U4 since this is the most important opamp.I only change U17 (tonesection) with a LT1058, not cheap but very good.

[shredbaron]

The depot thanks you 

Metal film will help keeping the noise down a bit.

Yeah the OPA2604 is harder to find since these are no longer made in PDIP housings.I did once replace all the opamp with 2604's and that was too much for me, sounded too hifi.For me I only change U4 since this is the most important opamp.I only change U17 (tonesection) with a LT1058, not cheap but very good.

Thanks - did some digging - going to try a OPA1644 with an adapter (it's SOIC14). Crazy specs (check 'em out) and not that expensive ($7.90 CDN)...although the adapter is almost as much as the chip :)