Armstrong A521 Amplifier

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gninnam
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#1 Armstrong A521 Amplifier

Post by gninnam »

Howdy all.

Thanks to Steve on here I have been tweaking with the free amp he gave me - the Armstrong A521 Amplifier (1968 to 1972).

Gave it a reasonable clean then powered it up and found that only one channel was working (as Steve had told me).
The amp is modular inside so I swapped the boards around (amp and controller) and still the 'A' channel failed, but the channels share the same power supply board so after comparing, noticed that it has 2 fuses on the power board, one was new(ish), while the other looked original - guess what - wrong, the old one was fubar.....

Replaced the fuse and all is now working :D

The issue with the amp is the AL102 transistor which is a Germanium PNP - now hard to come by, costly and also not too reliable (so I am told), but my test proved it works, just need some Servisol to clean the contacts and see what happens next!!

Will probably have to change a few of the caps (will be over 40 years old) but will have a play first!!

Oh, and a few pictures:

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Cheers
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shane
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#2

Post by shane »

I used to sell them. I feel old now...
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pre65
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#3

Post by pre65 »

I still have the 625 receiver that I purchased brand new in the late 60's. It was last used as my keyboard amp about 10 years ago. Can't bear to chuck it out. :wink:

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Nick
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#4

Post by Nick »

You probably know this, but Jim behind these pages is a good source of info.

http://www.audiomisc.co.uk/Armstrong/armstrong.html
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gninnam
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#5

Post by gninnam »

Cheers Nick, yep - this is what I used to help me fault find.
Loads of useful stuff on there :D
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chris661
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#6

Post by chris661 »

Talking of old SS equipment, here's mine...

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One day, I'll hook it up to those old eliptical speakers, see how bad that sounds. I replaced the PSU caps, as it was a single 2,200uF that was knackered. Now there's 2x3,300uF.
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pre65
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#7

Post by pre65 »

Like my Armstrong 625 it's got DIN sockets for inputs and speakers.

And a right pain they are. :wink:

This is what replaced the 625, a QED A240 CD with (gasp :wink: ) no tone controls.

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Mike H
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#8

Post by Mike H »

Arrrgghhh!!! Plug-in boards! :lol:


What's the issue with the AL102 transistor?

I noticed Cricklewood Elec stock quite a few germaniums, not sure about that one though.

 
 
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gninnam
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#9

Post by gninnam »

Mike,

Reading stuff about the AL102, they reckon it is hard to find one which is stable so will check mine out fully and see if they are all stable - if one or more do need replacing then I am sure I saw some on Evilbay at around £20 or so!

Andy
Mike H wrote:Arrrgghhh!!! Plug-in boards! :lol:


What's the issue with the AL102 transistor?

I noticed Cricklewood Elec stock quite a few germaniums, not sure about that one though.

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pre65
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#10

Post by pre65 »

Is the end result likely to be worth spending any money on it ?
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gninnam
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#11

Post by gninnam »

Possibly not, but hate seeing things which for a small outlay, can make it sing again (and I like the look of it too. :shock:
pre65 wrote:Is the end result likely to be worth spending any money on it ?
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Mike H
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#12

Post by Mike H »

Please Sir, how do you test whether an AL102 is stable?


 
 
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Mike H
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#13

Post by Mike H »

Would've thought actually could find a more readily available equivalent to the AL102? Replace the lot :?:


 
 
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gninnam
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#14

Post by gninnam »

All good questions Mike - was going off the info on the Armstrong link mentioned above.

Will have to play it by ear (so to speak) and fire it up with proper speakers (was testing it with some surround speakers (4 Ohms) - will have a play tomorrow.
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ed
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#15

Post by ed »

I thought that looked familiar...I just had to get the screwdriver out and be nosey...:

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and

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its a leak delta30

outputs are rca 16006 and this site lists equivs(RCA 16006 = 2N3055) for some, might be useful:

http://www.divdev.fsnet.co.uk/repair5.htm
Last edited by ed on Thu Jul 15, 2010 12:29 pm, edited 1 time in total.
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