Metropoulos Forum

Yeah, that's the aa763 - those are rare and valuable

Roe wrote:Yeah, that's the aa763 - those are rare and valuable

Thanks Roe

Good to know they are rare and valuable. The amp holder told me he has to be very careful if he is doing gigs with this amp. Someone has always to keep an eye on it.

Daniel

Hi forum members

Do I have to swap the brown Astron tone caps on the main circuit board: https://www.dropbox.com/sh/fy1uup7kduem ... G_3797.jpg? Can they get bad over time? The blue molded I think rarely need replacement, isn't it so?

Any related input is welcome! Thanks,

Daniel

Are you referring to the big, round electrolytic caps on the board? If so, then yes...it's a good idea to swap those also as they are way past their useful life. I also saw a brown drop on your board I believe. They are film caps and they do not suffer the effects of time like electrolytics do.

danman wrote:Are you referring to the big, round electrolytic caps on the board? If so, then yes...it's a good idea to swap those also as they are way past their useful life. I also saw a brown drop on your board I believe. They are film caps and they do not suffer the effects of time like electrolytics do.

Hi danman

Thank you for your response. Yes, referring to the big oily paper caps on the cathode: three of them have 2x25uF/25VDC
and one has 25uF/25VDC . I then will swap them too.

The smaller browny ones seems for me also that they are film caps. I let them as they are in.

Daniel

Yes...the 25uf/25v are well past their useful life. If the amp is a player, I would want to replace them with fresh caps.

danman wrote:Yes...the 25uf/25v are well past their useful life. If the amp is a player, I would want to replace them with fresh caps.

Thanks danman for your confirmation. The amp is a player and has to be it for further 25 or 50 years .

Daniel

Today I swapped the Astron tone caps (2x25uF/25 VDC) on the main board with new TAD's (2x25uF/25 VDC). After I soldered out the old brown Astron caps I measured them against TAD: Here the approximate values:

Astron: 45-70 uF and ESR 1.9-6.5 Ohm at 1 kHz (a very bad one has 8.5 nF nano! and ESR 28 kOhm kilo!)
TAD: 24-24.5 uF and ESR 0.11-0.12 Ohm at 1 kHz

It confirms, that the old Astron Caps has to be replaced with new ones. Enclosed a picture: https://www.dropbox.com/s/vvkjnvw1b8woy ... 8.JPG?dl=0

Daniel

The amp should sound great when your done!!

danman wrote:The amp should sound great when your done!!

Yes danman, it really sounds much better and the amp is more stable. Also there is less hum.

New filter caps: https://www.dropbox.com/s/t4eb1b1ypyv45 ... 2.JPG?dl=0
New tone caps: https://www.dropbox.com/s/x72xrnp5ejeru ... 9.JPG?dl=0
New bias cap: https://www.dropbox.com/s/3m4g1zt694t73 ... 7.jpg?dl=0
Additional grid stoppers: https://www.dropbox.com/s/qtu1aui87dg8j ... 8.jpg?dl=0

I hope my guitar friend is satisfied and happy with my job.

Only if I watch the small new bias cap I am a little bit scared. I hope it is a good one?!

Daniel

Thanks for sharing that.

Still hanker for a nice clean BF Fender, waiting for BFDR to fall into my lap in the same condition as that one!

neikeel wrote:Thanks for sharing that.

Still hanker for a nice clean BF Fender, waiting for BFDR to fall into my lap in the same condition as that one!

My pleasure! It was fun to restore such an old amp. Thanks to all of you who helped me to come through!

Don't know how many Blackface Vibroverb AA763 from 1963-64 are made by Fender? Anyway, I wish you good work on your Blackface Fender!

Daniel