ARCAM D290 DEAD - PLEASE HELP

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Hi. My amp for years, an ARCAM D290 just died on me. First problem was that it kept blowing the fuse. Then I searched on the forum for similar threads, found out that two of my output transistors were short (right channel). After removal of these transistors, I put in a new fuse, but still the amp is not switching on (No LED no nothing). This time the fuse is not getting blown and I can even measure most voltages, like the -+44vdc etc
What could it be guys, I thought of the protection circuit, please help. I have the service manual, but I am afraid not much in there to help me. TIA
 
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If you simply removed the output Mosfets, the protection circuitry will most likely still sense an error voltage at the amplifier output rail and prevent connection to the speakers, if a relay is fitted. Are you just guessing the Mosfets are blown because that seems similar to the fault in another thread? You could be right but there may be another reason for a protection fault. Do you actually measure a short across source-drain? If there are rail fuses in the faulty channel, remove them and see if the fault condition persists.

You may also want to check up on sources for replacement mosfets. I understand the originals are unobtanium and IRF240 (TO3 case) is indicated as a substitute. They are not exactly plentiful either but you'll need them first in any case.
 
If you simply removed the output Mosfets, the protection circuitry will most likely still sense an error voltage at the amplifier output rail and prevent connection to the speakers, if a relay is fitted. Are you just guessing the Mosfets are blown because that seems similar to the fault in another thread? You could be right but there may be another reason for a protection fault. Do you actually measure a short across source-drain? If there are rail fuses in the faulty channel, remove them and see if the fault condition persists.

You may also want to check up on sources for replacement mosfets. I understand the originals are unobtanium and IRF240 (TO3 case) is indicated as a substitute. They are not exactly plentiful either but you'll need them first in any case.

Thanks Ian. I can confirm that the mosfets that I took out are short. With a DMM on resistance mode, I am measuring about 36 ohms across all pins. I don't see any more fuses. What resistance should I get across the thermistor when the amp is off? I am getting about 1000 ohms, is it ok? Hope that helps.
 
For the Delta 290, the correct replacement MOSFET is IRFP240. Some modifications are required. The replacement procedure is in the service manual.

The service manual suggests the LED should lit if the +44V rail is available. It is a bi-colour LED which will change colour if the TA7317P thinks there is a fault. If you have not replaced the MOSFETs yet, it is quite likely that the amp circuits will not bias correctly and will have DC on the outputs. You can check that on the leg of R2/R102
 
Mine blew out a diode.. yup just one. Only orange LED lit up, no green.
Then the silly 'tech' substituted a normal as opposed to specified /oem slo blow fuse and the twit could not understand why it kept blowing.
This at a 'Factory Authorised' repair shop.
How was yours working previously?
Asking as I turned off the internal tone control/preamp section years ago and have no plans on ever turning it back on.
Doing this very noticeably improved the sounds. It' s now quite a good amp. Surprised me actually.
The tone defeat has almost No effect by direct comparison, seemingly it does not bypass the tone bits ?.
Curiously this is a Hi Gain design amp with a tone stack tacked on... but then that's true of most (all?) integrateds.
G'luck
 
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For the Delta 290, the correct replacement MOSFET is IRFP240. Some modifications are required. The replacement procedure is in the service manual.

The service manual suggests the LED should lit if the +44V rail is available. It is a bi-colour LED which will change colour if the TA7317P thinks there is a fault. If you have not replaced the MOSFETs yet, it is quite likely that the amp circuits will not bias correctly and will have DC on the outputs. You can check that on the leg of R2/R102

Hi Jaycee
Thanx for your input. Do you happen to have a link for that service manual? Yes I haven't changed the mosfets as yet. Its because I heard someone say their d290 also blew the outputs transistors for the right channel also, but when they tested the amp (before mosfet replacements), the amp switched on and amplified the left channel properly. I will measure with DMM and let u know (R2/R102)
 
Mine blew out a diode.. yup just one. Only orange LED lit up, no green.
Then the silly 'tech' substituted a normal as opposed to specified /oem slo blow fuse and the twit could not understand why it kept blowing.
This at a 'Factory Authorised' repair shop.
How was yours working previously?
Asking as I turned off the internal tone control/preamp section years ago and have no plans on ever turning it back on.
Doing this very noticeably improved the sounds. It' s now quite a good amp. Surprised me actually.
The tone defeat has almost No effect by direct comparison, seemingly it does not bypass the tone bits ?.
Curiously this is a Hi Gain design amp with a tone stack tacked on... but then that's true of most (all?) integrateds.
G'luck

Hi
Mine was working fine before this. Thanks for your input. If you figure anything new, let me know.
 
Hi
I saw service manual.
There are gate protection zener 15V, but are probably from lower to 6V2.
Also check drivers.

Ciao
Ho visto il sm
Ci sono zener da 15V a protezione dei gate, ma secondo me andrebbero sostituiti con dei 6V2 per maggior sicurezza su carichi bassi.
Controlla i drivers.
 
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For the Delta 290, the correct replacement MOSFET is IRFP240. Some modifications are required. The replacement procedure is in the service manual.

The service manual suggests the LED should lit if the +44V rail is available. It is a bi-colour LED which will change colour if the TA7317P thinks there is a fault. If you have not replaced the MOSFETs yet, it is quite likely that the amp circuits will not bias correctly and will have DC on the outputs. You can check that on the leg of R2/R102

Jaycee
Apparently I am not getting a DC voltage on R2 or R102. Removed all mosfets now, but still the amp remains dead. No LED light no nothing. U seem to know a lot about this amp, owned one? Can u give a kind of a (voltage) guide here, I am stuck. If you can tell me where to measure and what. will this amp at least switch on (even orange led), if mosfets are not present? How much AC should get on the yellow wires from the transformer? Let me know. Thanks
 
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Whilst waiting for Jaycee, you could refit the mosfets that are OK in the other channel. It is good to have one working channel to compare with the one that isn't. That will help greatly to track any faults. You could also obtain the replacement IRFP240s, perhaps some spare T0247 or TO-3P insulator washers, heatsink grease etc.

Actually, there should not be any voltage at R2 or R102 ( the output) so at least you know there is less chance of damage in the amplifier.
 
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This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.