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Richard Allan Class A (Sugden A21) rebuild

Discussion in 'classic' started by Arkless Electronics, Apr 18, 2018.

  1. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    This was a job for a fishie of this parish and as it's a pretty rare classic and the first ever SS class A integrated amp (AFAIK) I thought people may find it interesting.

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    Above shows the state of some of the original caps...

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    This is the pre amp section before work. The preset resistors allow the bass and treble controls to be trimmed so that they are genuinely "flat" when set at "12 o clock"!

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    Observe the broken resistor which once formed a mains suppressor in conjunction with the Mullard "dog bone" capacitor.... This is the first and only time I've known one of these caps to fail and in this case it wasn't surprising as it was nowhere near high enough rated for the voltage. It was a 400V DC cap and needs to be at least a 630V DC cap for this use!

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    A few pics showing the total strip down that was needed to properly do the work... It's a twat to work on! The mains transformer has to be disconnected and unbolted just to get at the fasteners to remove other parts as a small illustration :mad:

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    A pic of one channel of power amp showing interesting extra tracks and un-drilled holes which suggest it was/could have been used for another model also...

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    New speaker sockets fitted...

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    Re-capped power amp boards...

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    Re-capped pre amp board and new modern suppressor cap across on-off switch...

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    New smoothing caps and speaker coupling caps are rather smaller than the originals! Despite having over twice the voltage rating!

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    .... which meant having to replace some of the wiring loom to accommodate them...

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    A few hours later...

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    Cleaned front panel and pre amp screening cover back in place.

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    The finished unit:)

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    Some of the old gubbins which was replaced...
     
    ff1d1l, pure sound and martin clark like this.
  2. Tony L

    Tony L Administrator

    Excellent stuff. A lovely amp IMO, a friend has a Sugden branded one and the more powerful A51 power amp.
     
  3. calorgas

    calorgas Ratty bumpkin

    I had one of the old Sugden a21’s too (and the much later a21a).
    Are there any differences between the Suggie and the RA versions? I enjoyed my a21 but I thought the a21a was quite a step up and forward from the original. Looks great though
     
  4. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    All parameters were checked over, such as class A standing current, tone control trimmer settings, etc etc and amazingly nothing needed touching! It took some time doing all the tests for frequency response accuracy at "tone controls flat", balance accuracy etc and knobs were carefully fitted to controls so that, for example, the channels were truly matched with the balance control at "12 o clock".

    All controls and switches were well cleaned out with IPA before being treated with contact cleaner and this has brought them back yo as new condition in this case... no crackles or anything...
    Output devices re-torqued down as fasteners were a little loose, DIN sockets cleaned out etc... The mains TX was originally at a jaunty angle due to bent fixing lugs,( possibly took a beating in transit at some time? These are built like a brick outhouse so it would have took some beating to do it!!) and this has also been sorted...

    There are some interesting touches that Sugden did in this such as the central steel strip which holds the smoothing caps etc is held in place with insulated nylon bolts and insulating washers at one end to avoid the steel strip causing a ground loop! Nice;)

    So what does it sound like? REALLY good actually! Vastly better than an all original unsorted MkII version I sold a few years ago... So pretty much like a A21se but only 10WPC.... It would, IMHO, trounce a Quad 33 and 303 for example...
     
  5. calorgas

    calorgas Ratty bumpkin

    Haha, that’s fighting talk where I’m from :D
    In hifi terms ‘trouncing’ can usually be translated as ‘can possibly discern a subtle difference that one person may prefer over another, but no guarantee the next person will agree’. ;)

    But as I said, it looks great and I bet it sounds even lovelier.
     
    Sashmo and lexi like this.
  6. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Jim's site has all the info on the differences etc ("Jim misc")
     
  7. monstrous lie

    monstrous lie Infinitely Baffled

    What a great little unit - I have a soft spot for early Sugden kit!
    And a smashing rebuild job too, Jez.
    ML
     
  8. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Cheers!:)

    It's been on all afternoon now and seems to just be getting better as the new caps "bed in"... Listening to "Jazz at the Pawn Shop" on vinyl via Arkless Transconductance phono stage into "Tape" on Sugden at the moment and it sounds better than it has any right to!!:eek::) This would worry some very expensive modern amps;)
     
  9. sq225917

    sq225917 Bit of this, bit of that

    Just think how much better it could have sounded if you'd used to some propper "audiophile approved" fuses in it...
     
  10. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    ... it would surely have Krell shitting themselves if I'd fitted those:D
     
    sq225917 likes this.
  11. Tony L

    Tony L Administrator

    I’d have polished and Deoxited the ones that are there! All my equipment fuses gleam, as do their holders!
     
  12. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Ah well I did polish the originals before adding a drop of contact cleaner;)
     
  13. Pete MB&D

    Pete MB&D Pete Maddex, the one and only!

    Takes me back to my TV repair days those mustard Mullards and carbon resistors, just needs 20 valves and a convergence panel!

    Pete
     
  14. Tigerjones

    Tigerjones Bagpuss

    My wooden sleeved Mark 1 version of the A21 is the one piece of kit I would never sell. Glorious amplifier with a great phono stage. It just requires fairly careful speaker matching.
     
  15. hairyderriere

    hairyderriere pfm Member

    Have you ever worked on refreshing an original Sugden A21 and matching R21? I have both in need of some TLC...
     
  16. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Erm... this is an original Sugden A21.... The badging on it and styling was changed to Sugden after a short while... the only difference is the front panel.

    As I regularly remind fishies I refresh/repair/rebuild and re-cap ALL makes and models of analogue hi fi equipment, be they valve, transistor, mosfet, point to point wired or PCB, ancient or modern... at my discretion of course as there will be the odd specific models here and there that are just such a PITA to work on that I won't take them on.

    Obviously unless a specific item of equipment has become a collectors item it will always cost considerably more than the present second hand value of the unit to have it refurbished. IE just 'cos you can buy a 1970 "Acme MkII" power amp from ebay for £120 doesn't mean it won't cost £300+ to rebuild (could be £180 or £400 etc much depends on what is required, how difficult to work on it is etc etc) as it would wherever you take it for such work done to this standard. One needs to think of it in terms of that in today's money the "Acme MkII" could well have been £1200 new and for say £300 you've got an example that is back to as good as new or better.

    Some of the kit I've rebuilt in the last few years includes Quad II's, Quad 303, Leak Stereo 20, Leak Varislope, Radford STA25, Pioneer SA-9500, Meridian 105's, Meridian M2's, Pye Mozart pre, power and tuner, various Musical Fidelity amps, just to name a few...
     
    Last edited: Apr 20, 2018
  17. hairyderriere

    hairyderriere pfm Member

    I was never sure if there were any changes between the Allan and the Sugden - guess you cleared that up! Cheers.
     
  18. martin clark

    martin clark pinko bodger

    Good for another 40yrs+. Lovely!
     
  19. Stunsworth

    Stunsworth pfm Member

    Lovely. It amazes me that unlike other brands from the 60s Sugden have managed to survived. I’ve no idea how they have managed that when so many others have disappeared.
     
  20. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Maybe not in quite the original form but I guess times change... Every unit was built by one person back in the day and Sugden were known for this. It's not the same now though as a mate of mine who's also an EE was working for a company in the north east who, amongst lots of other things, were making, stuffing and testing the boards for Sugden Master class gear a few years ago.... and another EE mate was working for a different NE firm who were doing the same for Arcam... Contract manufacturing companies... Probably had ECU's for cars on the next production line and burglar alarms on another...
     

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