Hi all!
Long time scroller, first time poster here.
I flippin love this forum - general thanks to all involved.
So: I got a cheap Audiolab 8000a on feebay.
Serial number is faded but looks like 667038.
It has Din sockets, and AFN8411 outputs - Early version.
Right channel has had magic fairy smoke escape predrivers, and some resistors.
I have not had a proper dig around yet, but seems to be a common problem.
Questions:
Any thoughts and opinions about the amp are welcome.
Thanks!
Long time scroller, first time poster here.
I flippin love this forum - general thanks to all involved.
So: I got a cheap Audiolab 8000a on feebay.
Serial number is faded but looks like 667038.
It has Din sockets, and AFN8411 outputs - Early version.
Right channel has had magic fairy smoke escape predrivers, and some resistors.
I have not had a proper dig around yet, but seems to be a common problem.
Questions:
- Does any kind (or not) soul have a Mk1 service manual?
- Anyone know anything about the AFN8411 mosfets? Very little info out there regarding replacements.
- Has anyone replaced blown predrivers / drivers / outputs on this model with new or available devices.
Any thoughts and opinions about the amp are welcome.
Thanks!
The 8000A schematic I am looking at doesn't have mosfets and you quote AFN8411 mosfets ???
Different era they are modern SOT-223 SMD power mosfets so somebody has either "played around with it " or is a Chinese "copy " which it seems are available .
http://www.alfa-mos.com/datasheet/MOSFET/AFN8411.pdf
Different era they are modern SOT-223 SMD power mosfets so somebody has either "played around with it " or is a Chinese "copy " which it seems are available .
http://www.alfa-mos.com/datasheet/MOSFET/AFN8411.pdf
Have looked at a number of manuals which don't match the outputs, nor the driver devices.
The diyaudio threads are mostly about Mk2's with the big sanken outputs - I will have another search session this evening though, thanks.
Thanks Duncan - could well be messed around with. PCB/Chassis is 100% genuine.
I hadn't spotted the 8411's are originally sot-223.
The ones in this amp are TO-220 - maybe fake.
However I checked the joints/installation - they look very original tbh.
audiolab 8000a
Interestingly, the link above details the same layout as mine, and the owner also has the AFN 8411.
On that post the wonderful AndrewT reckoned he had 'heard about' 8000a's that used BD outputs. That post was not resolved.
Maybe Audiolab had some early variations that aren't well documented.
If it was a Sanken version, I would restore - but this one might just get some LM3886 amps instead
Not too worried, just
I hadn't spotted the 8411's are originally sot-223.
The ones in this amp are TO-220 - maybe fake.
However I checked the joints/installation - they look very original tbh.
audiolab 8000a
Interestingly, the link above details the same layout as mine, and the owner also has the AFN 8411.
On that post the wonderful AndrewT reckoned he had 'heard about' 8000a's that used BD outputs. That post was not resolved.
Maybe Audiolab had some early variations that aren't well documented.
If it was a Sanken version, I would restore - but this one might just get some LM3886 amps instead
Not too worried, justIn the link you have provided one of the posters quotes the output devices as = SM8411 which is not the same as AFN8411 .
As that was their first amplifier the amplifier is dated to the early 1980,s which looking at the parts and those orange capacitors of the time that would be right , so if yours is the same then most of it is genuine .
OTOH those mosfet SMD output devices you quote were not sold at that time and an early German SMD -decoder book has Siemens SMBTA-43 in SOT 23 which are NPN BJT,s none of the SM range by them are mosfets or fets.
SOT223 is much later heavier build as AFN 8411,s arec output devices.
Taking that into consideration your output devices aren't --or shouldn't be mosfets .
As that was their first amplifier the amplifier is dated to the early 1980,s which looking at the parts and those orange capacitors of the time that would be right , so if yours is the same then most of it is genuine .
OTOH those mosfet SMD output devices you quote were not sold at that time and an early German SMD -decoder book has Siemens SMBTA-43 in SOT 23 which are NPN BJT,s none of the SM range by them are mosfets or fets.
SOT223 is much later heavier build as AFN 8411,s arec output devices.
Taking that into consideration your output devices aren't --or shouldn't be mosfets .
Ok, feel the need to clarify something for future searchers as there seems to be hardly any info out there for this:
There IS a version of the 8000a that uses TWO pairs of multisex output devices PER channel, labelled:
SM 8411 AL8AN and SM 8411 AL8AP
(I just took two out, cleaned, checked properly like I should have done initially - lessons learnt ).
The PCB , Circuit is the same as amps using 1 2SA1216 and
1 2SC2922 per channel.
Search AL8AN in this repair diary for another account (no affiliation or adverts in that link):
Repair Briefs 5
They are also used in some Arcam Delta Integrated amps.
Now... Anyone got a datasheet for SM 8411 AL8AP / N so I can see if a TIP or MJ will work? !
There IS a version of the 8000a that uses TWO pairs of multisex output devices PER channel, labelled:
SM 8411 AL8AN and SM 8411 AL8AP
(I just took two out, cleaned, checked properly like I should have done initially - lessons learnt
).The PCB , Circuit is the same as amps using 1 2SA1216 and
1 2SC2922 per channel.
Search AL8AN in this repair diary for another account (no affiliation or adverts in that link):
Repair Briefs 5
They are also used in some Arcam Delta Integrated amps.
Now... Anyone got a datasheet for SM 8411 AL8AP / N so I can see if a TIP or MJ will work? !
Update/correction: its a different circuit than any 8000a with sankens.
Same Mpsa drivers, but different resistors values.
Also, 1x ztx 653, 753 and 450 per channel ( 2X 653 and 753 in sanken version).
Also also, the plethora of BC546/556 are b variants (these are c's in other versions).
It will cost about £30 for new amp transistors (same ztx & mpsa, tip42xc's for output, spare BC's), supply capacitors, and a few other dodgy caps and burnt resistors.
Worth resurrecting? I'm not convinced....
These amps have a fixed 220v primary winding. Its a part of the failure rate ( for Irish 239V mains, the amp gets an extra few volts DC).
Other reasons:
Generally, the A60 seems better engineered, in some respects. Having recapped one carefully, and applied good thermal paste, it does not get hot at moderate volume and runs stable (plus wooden case).
Having said that, I will probably attempt repair!
Soft spot for vintage British gear.
Will stick to Elvee's circlophone for daily aural pleasure however
Same Mpsa drivers, but different resistors values.
Also, 1x ztx 653, 753 and 450 per channel ( 2X 653 and 753 in sanken version).
Also also, the plethora of BC546/556 are b variants (these are c's in other versions).
It will cost about £30 for new amp transistors (same ztx & mpsa, tip42xc's for output, spare BC's), supply capacitors, and a few other dodgy caps and burnt resistors.
Worth resurrecting? I'm not convinced....
These amps have a fixed 220v primary winding. Its a part of the failure rate ( for Irish 239V mains, the amp gets an extra few volts DC).
Other reasons:
- The output device heatsink fins are the only ventilated part. Like the Arcam A60. But inside achieves higher temps.
- Tiny, mini predriver heatsinks are glued on - they fall off due to heat. Not great sinking of heat.
- Power supply ground/live and speaker output cable routing is dire.
- Resistors, drivers, caps are all squashed together - no air to breath.
- Prone to oscillation on early versions, by some accounts.
Generally, the A60 seems better engineered, in some respects. Having recapped one carefully, and applied good thermal paste, it does not get hot at moderate volume and runs stable (plus wooden case).
Having said that, I will probably attempt repair!
Soft spot for vintage British gear.
Will stick to Elvee's circlophone for daily aural pleasure however
Hi Kaibosher, I have rebuilt a number of Audiolab 8000a and yes there are a number of variants. I have attached the earliest service manual I have been able find.
Output devices were originally Sanken 2SA1216 and 2SC2922, the large double sized package which have been discontinued. I have successfully used Sanken 2SA1386A and 2SC1386A available from Digi-Key.
Worth a rebuild, I run the bias a little higher than suggested but as you mention Audiolab worked on the principal of a closed box to get all components up to temperature and a number of them suffer. Especially the three 4K7 resistors in each driver circuit which burn the circuit board. I replace these with a single 1K5 3W and stand it well off the board.
cheers
Output devices were originally Sanken 2SA1216 and 2SC2922, the large double sized package which have been discontinued. I have successfully used Sanken 2SA1386A and 2SC1386A available from Digi-Key.
Worth a rebuild, I run the bias a little higher than suggested but as you mention Audiolab worked on the principal of a closed box to get all components up to temperature and a number of them suffer. Especially the three 4K7 resistors in each driver circuit which burn the circuit board. I replace these with a single 1K5 3W and stand it well off the board.
cheers
Update:
6 blown pre's, drivers, and outputs - bc546, ztx653, mpsa42, and AL8AN / P.
5 bad resistors too.
Basically, one side of that channel taken out.
Referring back to Repair Briefs 5 ...
These early amps seem prone to oscillation. That link describes adding some decoupling electrolytic's before the predrivers,
(There are no amp decoupling caps in this version - 47uf is added later).
I'll try to repair and see if it makes bad shapes before any modding.
6 blown pre's, drivers, and outputs - bc546, ztx653, mpsa42, and AL8AN / P.
5 bad resistors too.
Basically, one side of that channel taken out.
Referring back to Repair Briefs 5 ...
These early amps seem prone to oscillation. That link describes adding some decoupling electrolytic's before the predrivers,
(There are no amp decoupling caps in this version - 47uf is added later).
I'll try to repair and see if it makes bad shapes before any modding.
I've never had any oscillation but you're right there is a mod to add decoupling caps across the 12v zenners. Make sure you rate them higher than the main rail voltage. First time I just grabbed what I had, 47uf 16v, well they are only 12v zenners. Two of them went short on me after a week and I thought from the sound I had killed a speaker but it survived. Interesting about the Two x 220s, has someone used two of these in place of the original MT200?
Attachments
Nah this amp definitely utilized 220 types from factory. I speculate Audiolab used to220 Sankens in very early editions, ran out, then used AL8A for a short while before updating the circuit for larger (and less) devices.
Check out package list on page 6 of 'model 207' manual.
The MT200 type outputs are something like dual transistor sziklai pair packages, and replaced the individual sziklai paired AL8A.
There is no room in there for anything but 220's, look how tight it is in attached photos!
Check out package list on page 6 of 'model 207' manual.
The MT200 type outputs are something like dual transistor sziklai pair packages, and replaced the individual sziklai paired AL8A.
There is no room in there for anything but 220's, look how tight it is in attached photos!
Attachments
Wow that is not a version I have seen and I have a few. The TO 220s referred to in page 6 of the 207 manual are the driver transistors, not the output and in the versions I have are bolted to separate heatsinks that sit on top of those little ztx's. Your version must have been quasi complimentary output with two transistor in parallel. There is an earlier link showing the same design audiolab 8000a plenty of pictures but not a lot of info.
Ah ok - I've only seen pics with the heatsink obscuring the driver. Makes sense now thanks.
That link is one of precious few references to this early amp online.
Found another here: Help! Audiolab 8000A
Again no schematics. Outputs replaced with BD911/912 s.
I will attempt a circuit drawing, might be useful to someone in future.
That link is one of precious few references to this early amp online.
Found another here: Help! Audiolab 8000A
Again no schematics. Outputs replaced with BD911/912 s.
I will attempt a circuit drawing, might be useful to someone in future.