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A&R Cambridge A60 - rebuild thread

That's a great point. I have just looked at the schematics and even from 'Issue 8 serial 25502-' it still shows the rail to be 35v.

However the caps installed are definitely 50v. They must have done that for a reason so am I best leaving it all as is rather than replacing with 35v (or even 50v). Electronics are not my thing!

Paul
 
Certain long established English amplifier manufacturers seem to fit capacitors with no derating at all, but most of us would use 50V on a 34V nominal rail, the extra cost is negligible compared to a blown speaker from a fault
 
Soldering finished. Swapped four 63v 22uF caps and the 4 resistors.

Re-assembled and...whaaahhhhhh. Power supply fuses blown straight away :-(
Took the board out and check everything. Joints looked good, length of wire looked good.

Connected it up again on the bench (NOT in the chassis) all good.

Put it back in the chassis - blown again. Must be shorting out somewhere on the chassis?

Anyone got an idiots guide to tracking this down? I tried using the mutlmeter to see if anything obvious is earthing but can't find it.

Help please
 
I am a complete idjut

Here is my beginners mistake : When you screw in those TIP3055s to the heat sink you need to ensure the screws are insulated correctly - hence those little black plastic 'washers'. Whatever you do, don't forget to make sure they are all fitted correctly. Doh!


vinyl_paul said:
Soldering finished. Swapped four 63v 22uF caps and the 4 resistors.

Re-assembled and...whaaahhhhhh. Power supply fuses blown straight away :-(
Took the board out and check everything. Joints looked good, length of wire looked good.

Connected it up again on the bench (NOT in the chassis) all good.

Put it back in the chassis - blown again. Must be shorting out somewhere on the chassis?

Anyone got an idiots guide to tracking this down? I tried using the mutlmeter to see if anything obvious is earthing but can't find it.

Help please
Click to expand...
 
I might well offer them out, depending on if I decide to use them or plump to buy new 50v versions instead. Can't make up my mind.

Most people seem to use 35v on the 34v rail so I guess I will be ok to give them a go? Otherwise I'll let you know!

grazie said:
If you're serious, I'll take them if the price is right. ;)
Click to expand...
 
vinyl_paul said:
I am a complete idjut

Here is my beginners mistake : When you screw in those TIP3055s to the heat sink you need to ensure the screws are insulated correctly - hence those little black plastic 'washers'. Whatever you do, don't forget to make sure they are all fitted correctly. Doh!
Click to expand...

Just to clarify, not just the screws, the whole component (other than the connection legs obviously) needs to be insulated.
 
Hi Julian,
I have double-checked my board (a newer version 10) and they are definitely *both* showing as 50v 10uF

Examples of the orange variant are: c7, c107, c22, c122
Examples of the blue variant are: c14, c114, c19, c119

No idea why they are different or if I can change them both for the same 50V 10uF?


Operajulian said:
The orange ones were a different voltage and uF range to the blue ones. Most of the 'thin blue ones are 10uF - 35 volt.
The oranges are thin 4.7uF 10 volt or fatter 47uF 10volt.

Replace them all with the same value uF Panasonics or if you want to to go "posh" then use WIMA films.

I tried bypassing the tone controls on one and it really made no audible difference. ( bit like the extensive use of WIMA's ) but if so inclined try it if you like it....

Julian
Click to expand...
 
Hi there Vinyl Paul:
I suspect it was all to save on component prices. Lower voltage rating is slightly cheaper, even a few pence over thousands and thousands of amps makes quite a difference.

If you look at the circuit diagrams for later series all the ones you list were 10uF with either 40v rating or 50v rating. So I think you are fine to change them all to 10uF 50v.

In earlier series, C7 and C22 for example were 47uF 10v.

Julian
 
Its nice to see people making classic old stuff work again, well done.
I just wish I had more electronic skills so I could do this my self
 
So.... 2015 and I'm restoring my A60 and T21.

I've looked for Robert's further articles regarding repairing a blown channel and restoring the T21 but can't find them anywhere. Were they never completed?

Also, is his article still relevant - i.e. have his suggested capacitors been improved upon since 2008?

I'm a bit of a novice solderer but would really appreciate a 'how-to' on the blown channel repair and T21 restoration.

Thanks in advance.
 
Hi I'm currently preparing to recap my A60. I've read through all the posts and made a list of most components.

I'm just missing what replacements to use for TIP3055?

My A60 is currently dead (thats what you get for lending it to my daughter lol) and i suspect the same 2 transistors that where replaced on your A60, or at least something on that channel.

Thanks
 
You need to be careful which TIPs you use, Audio Amplifier Servicing who has a YouTube channel has the correct ones in stock, he usually fits them, but he may sell you two.
 
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Geoffreybombom said:
You need to be careful which TIPs you use, Audio Amplifier Servicing who has a YouTube channel has the correct ones in stock, he usually fits them, but he may sell you two.
Click to expand...
I've watched his videos on the A60 and the A60 he used also has 2 blown tip3055's lol

I have emailed him about the TIP's

Thank you
 
If you can afford it, I would get him to repair it, he is very good, his name is Gary, lives in Wolverhampton, no relation, I am just a previous customer. Also his prices are very reasonable.
 
Geoffreybombom said:
If you can afford it, I would get him to repair it,
Click to expand...
Now wheres the fun in that :D

Although this is my first amp repair i've been messing around with electronics for years and it'll be a pleasure working on the A60. unlike modern tiny electronics i can see.
 
Ako said:
Now wheres the fun in that :D

Although this is my first amp repair i've been messing around with electronics for years and it'll be a pleasure working on the A60. unlike modern tiny electronics i can see.
Click to expand...
I bought a broken (but evidently high end) CD player from a car boot.

This:

Toshiba XR-Z90

from 1982-83. It's through-hole, but everything's rather small. You can use the DIP packages for scale.

aa by plybench, on Flickr

Fortunately, I just scavenged it for (very nice) parts.
 
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