Revox Preset Trimmers....and Electrolytics??

[tonewheelkev]

Hi All
Think it's about time I delved further into my B77....do some serious updating.
Concerning preset pots....have spotted 'kits' on Revox specialist sites...but wondering if there are possibly cheaper (? ) alternatives?

Same with Electrolytics really....I have a local RS counter....and a huge range to choose from. I'm thinking that lifetime is an important criteria here when making a choice....what do you think?
Any recommendations on brand/series please?

I thank you....!

[ben]

My advice is don't go swapping stuff for the sake of it, unless you want to introduce new problems. I know on the A77 there have been problems with those non-enclosed pots that fall to pieces, I wasn't aware of that on the B77. I use Piher types which are readily available.

As for capacitors, the RIFA ones on the motors and switches give problems but I am not aware of any widespread change-on-sight problems with electrolytics in the B77. I'm sure others will correct me there if need be!

It would be helpful if you could give us an idea of the fault symptoms.

If your criteria for this replacement work is simply age, then you might also have to swap out all those old resistors, transistors, heads, motors etc

[tonewheelkev]

Thanks....but it really is just component selection advice that I'm wanting
....particularly wrt Electrolytics?

[Ted Kendall]

Panasonic FC is safe choice, but Ben has a point - there's not a lot of point ripping through changing everything if it's working well. I've known the motor run caps to start leaking - worth checking for black goo.

[tonewheelkev]

Originally Posted by Ted Kendall

Panasonic FC is safe choice, but Ben has a point - there's not a lot of point ripping through changing everything if it's working well. I've known the motor run caps to start leaking - worth checking for black goo.

TBH....it isn't really working well...crackling, imbalances from L to R, noticed some wipers have dropped off presets!

Thanks for Panny FC headsup....the example I checked has a lifetime of 5000h.
How important is lifetime please?....I can see Wurth Electronik (at my local RS) with 10,000h....hence my lifetime query!!

[Ted Kendall]

A lot of that sounds like dirty switches, although crumbling presets should obviously be changed. With regard to electrolytics, it's best to go for 105C rating rather than 85C, which will give you a longer lasting cap to start with - note that the lifetime is at the quoted temperature, and if I remember right, lifetime deteriorates with temperature at something worse than an inverse square law.

I've used FCs in production for a long time and have never had to change one - YMMV, of course, but it's a reliable cap.

[tonewheelkev]

Originally Posted by Ted Kendall

A lot of that sounds like dirty switches, although crumbling presets should obviously be changed. With regard to electrolytics, it's best to go for 105C rating rather than 85C, which will give you a longer lasting cap to start with - note that the lifetime is at the quoted temperature, and if I remember right, lifetime deteriorates with temperature at something worse than an inverse square law.

I've used FCs in production for a long time and have never had to change one - YMMV, of course, but it's a reliable cap.

Yup....a whole lot of cleaning to do.
Didn't realise that lifetime reflected operation at a quoted temperature....had just assumed that it was down solely to hours of use.
Okay....that makes a lot of sense now!!

Thanks again...

[Michael Maurice]

I've had the tantalum caps go leaky. On the input board, it causes DC on the input level controls which cause crackling/static when you turn the controls.

[tonewheelkev]

Originally Posted by Michael Maurice

I've had the tantalum caps go leaky. On the input board, it causes DC on the input level controls which cause crackling/static when you turn the controls.

Tants are all going....you'll (well may) be glad to know!
Thanks