Hi All
I have been given a Summit Audio MPC100A , Reported fault is no output
On checking i can see that 3 watt 75R resistor is getting so hot its dropped out the board
There are 2 modules OP1- OP2, one or both are Bad, Can see that one is burnt up
I have no diagram and probably won't get one
I have contact summit audio, but don't expect a reply
Do you know where i can get replacement output modules
many thanks
JB
I have been given a Summit Audio MPC100A , Reported fault is no output
On checking i can see that 3 watt 75R resistor is getting so hot its dropped out the board
There are 2 modules OP1- OP2, one or both are Bad, Can see that one is burnt up
I have no diagram and probably won't get one
I have contact summit audio, but don't expect a reply
Do you know where i can get replacement output modules
many thanks
JB
Hi,
The modules are 'SA990', Summit own version of discrete aop '990' ( John Hardy's daop).
You need to contact Summit about them as you won't find substitute or can't use an other 990 kind to replace them.
They are most probably nested within a dc servo loop ( servo opamp is a op297 or op97) and there is some adjustements needed ( trimpot for the op297 probably the one on the upper left in your picture).
I've got a procedure description if you need it.
Is there a studio near your location? If there is try to reach the one responsible for maintenance in the crew and ask him if he can contact Summit for you, it might help to source the SA990. Sometimes it makes access to schematic easier too but i would not bet too much on it... worth a try though.
The modules are 'SA990', Summit own version of discrete aop '990' ( John Hardy's daop).
You need to contact Summit about them as you won't find substitute or can't use an other 990 kind to replace them.
They are most probably nested within a dc servo loop ( servo opamp is a op297 or op97) and there is some adjustements needed ( trimpot for the op297 probably the one on the upper left in your picture).
I've got a procedure description if you need it.
Is there a studio near your location? If there is try to reach the one responsible for maintenance in the crew and ask him if he can contact Summit for you, it might help to source the SA990. Sometimes it makes access to schematic easier too but i would not bet too much on it... worth a try though.
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I just took a look at my schematic collection and i've got schemo of TLA100.
The 990 are used as line drivers in these one and i would expect the same from the MPC100 ( at least the 75r resistor is present too and the adjusting trim should be 20k).
It's always funny to see those advertised as tube compressor when there is a vca ( or maybe an optocell) and the tube is only 'one stage' ( common cathode followed by cathode follower) within an ocean of opamp. 🙂
The 990 are used as line drivers in these one and i would expect the same from the MPC100 ( at least the 75r resistor is present too and the adjusting trim should be 20k).
It's always funny to see those advertised as tube compressor when there is a vca ( or maybe an optocell) and the tube is only 'one stage' ( common cathode followed by cathode follower) within an ocean of opamp. 🙂
@krivium sorry to revive this thread from a few years ago! I have a similar issue with my MPC-100a I think. I bought this off of reverb as the seller told me his tech said that it just needed its power supply re-capping. I recapped and it still had the issue of blowing the F1 fuse. Doing some research led me to Summit Audio's own FAQ webpage suggesting that the output DOA's are likely the culprit. I wasn't keen on giving Summit $135/piece for rebranded JH-990's so I have ordered 990's from Hairball Audio in Seattle which are based more directly on the original Deane Jensen design:
https://www.hairballaudio.com/catalog/parts-store/discrete-op-amps/je-990-discrete-op-amp
I reached out to John Hardy himself--very nice and genial guy--and tried to order some of his JH-990's but he's kind of gone off radar--hasn't responded to emails for about 5 months. so I'm going to try the Hairball ones.
Can you elaborate on the procedure for the adjustments needed? I am new to DOA's. Did John Hardy change much from the original design?
https://www.hairballaudio.com/catalog/parts-store/discrete-op-amps/je-990-discrete-op-amp
I reached out to John Hardy himself--very nice and genial guy--and tried to order some of his JH-990's but he's kind of gone off radar--hasn't responded to emails for about 5 months. so I'm going to try the Hairball ones.
Can you elaborate on the procedure for the adjustments needed? I am new to DOA's. Did John Hardy change much from the original design?
...and you're right. Looking at this design, they have two "E-cells" in the compressor circuit. Very mysterious! I am guessing that they are opto cells? For each of their different boxes they seem to have different components like this: the TLA-100 has a C-cell, the DCL-200 has a D-cell, and the MPC-100 has an E-cell. Definitely not a true valve compressor. I think the two valves in the circuit are a color "drive" circuit. I would guess at least they arent a starved plate arrangement. That was all the rage when this box first came out in the 90's.
Hi,
Sadly you'll have to cancel your hairball order as Summit sa990 are not compatible with other 990 ( and not all doa containing 990 into their names are compatible between themself...).
There is to my knowledge no workaround over the requested 135$ for an sa990 if you want to put your mpa back in working order.
Anyway check your pm i'll send you the calibration procedure.
And never believe 'my tech told me -insert whatever ********-' if it was as easy as a full recap the gear won't be on sale faulty for (not) cheap ( enough) on reverb as the 'tech' would had happily done for a small investissment of time and money.
Sadly you'll have to cancel your hairball order as Summit sa990 are not compatible with other 990 ( and not all doa containing 990 into their names are compatible between themself...).
There is to my knowledge no workaround over the requested 135$ for an sa990 if you want to put your mpa back in working order.
Anyway check your pm i'll send you the calibration procedure.
And never believe 'my tech told me -insert whatever ********-' if it was as easy as a full recap the gear won't be on sale faulty for (not) cheap ( enough) on reverb as the 'tech' would had happily done for a small investissment of time and money.
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Yes they are opto cells. Differents names for smoke curtains... like shredding parts number on components... you know proaudio is not immune to this kind of things...
Anyway i would not say it's not a tube compressor: it's a compressor and use a tube in the circuit. 😉
An LA2a is just that... an opto with a tube gain stage. Summit gear is more 'modern' approach: it is Doa (gain?) line driver stage and a tube stage to add 'color'.
TL Audio was using same approach as SPL or others... sure they aren't varimu design but they are not advertised as such either... and to be fair when working Summit gear sound great.
Using a DOA as line driver is a good way to lower bills of material as you don't have to use a transformer on output. Sound more transparent too ( what Manley do with their 'NuMu' too to atract 'modern' music customers feeling the original VariMu to be too much 'colouring').
It's all design choices... in the end what matters is how the gear sound, and yours sound good despite marketing half lies.
Anyway, if like the TLA100, the tube stage is typical common cathode into a cathode follower stage. Polarised around 200v. Not starved tube atrocity.
Anyway i would not say it's not a tube compressor: it's a compressor and use a tube in the circuit. 😉
An LA2a is just that... an opto with a tube gain stage. Summit gear is more 'modern' approach: it is Doa (gain?) line driver stage and a tube stage to add 'color'.
TL Audio was using same approach as SPL or others... sure they aren't varimu design but they are not advertised as such either... and to be fair when working Summit gear sound great.
Using a DOA as line driver is a good way to lower bills of material as you don't have to use a transformer on output. Sound more transparent too ( what Manley do with their 'NuMu' too to atract 'modern' music customers feeling the original VariMu to be too much 'colouring').
It's all design choices... in the end what matters is how the gear sound, and yours sound good despite marketing half lies.
Anyway, if like the TLA100, the tube stage is typical common cathode into a cathode follower stage. Polarised around 200v. Not starved tube atrocity.
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Thanks for that info and for the alignment pdf! I do know for a fact having spoken to John Hardy directly that for the last 7 years JMP (who make Summit stuff now) have been using his 990's in all their equipment, just with no markings on the top (I assume so they dont have to pay him more for his brand). What I don't know is the difference between a newer unit and an older one, which I think my MPC might be. The copyright on the PCB is 1996 (c), so I don't know if there have been revisions to that circuit in the last 7 years or not. Impossible to know without the schematics from Summit which they seem to be very cagey about. Can't find MPC schems anywhere and apparently they only provide them to techs with credentials?
Well i can't say, i've been away of this kind of gear for too long now.
I would not expect too much differences between older and newer units though. Yes Summit didn't share schematics, even when serial was given to them ( already faced this 15 years ago...): they had 'certified tech center' where you had to send units to be serviced iirc. Bad business model imho.
Anyway all i can tell is the potting and enclosure used to hide the circuit is responsible for faillure: heat accumulate and they eventually cook their components... it is same issue with 2520 and other doa using same mirror of smoke in hope to keep schematics secrets.
I would not expect too much differences between older and newer units though. Yes Summit didn't share schematics, even when serial was given to them ( already faced this 15 years ago...): they had 'certified tech center' where you had to send units to be serviced iirc. Bad business model imho.
Anyway all i can tell is the potting and enclosure used to hide the circuit is responsible for faillure: heat accumulate and they eventually cook their components... it is same issue with 2520 and other doa using same mirror of smoke in hope to keep schematics secrets.