Carver PM1.5 capacitor replacement

[jifop]

hi all!

i have a carver PM 1.5 amplifier with i suspect a dead voltage Regulator however i noticed that 4 of the large caps are bulged and dried up, according to the schematics however the four in question were originally two 2200micro 50/80v dual core capacitors which are no longer available. they have already been replaced with 4 separate caps wired up like the dual ones. but the thing is replacement radial electrolytics are about 20mm diameter max but the current ones are huge are the smaller ones correct or are there some specialist caps i should be using?

thanks

tim

[EchoWars]

Newer electrolytic caps are generally much smaller than those of even 10 years ago.

but the current ones are huge

Define 'huge'.

A new Nichicon HE 2200µf 50V electrolytic can take almost 3.7A of ripple current, and a new Nichicon VR 2200µf 100V cap can take 2.4A of ripple.

[jifop]

Thanks for your reply

theyre not huge actually, 50mm diameter 70mm long compared with the new ones of 18mm x 25mm! so will they do the job adaquately?

also i can't easily get 80v 2200micros, would 100v caps do? or do the ratings need to be identicle to the originals?

[tiltedhalo]

Hi jifop, capacitor failure is not an uncommon thing in 1.5 under extreme usage and time, but check for AC leakage you could have a bad diode in the low or mid voltage supply rails, or something could be a little off in the voltage tracking circuit for the triac or even some shorted windings in the field coil.
The two large 130VDC capacitors should also show signs of distress if a coil or voltage tracking problem is underfoot, the voltage tracking is taken of the high voltage rails.
As for replaceing the dual voltage caps due to modern size reductions it is easy to etch a small PC board and use separate low and mid voltage caps with better rateings then the originals in the same space.
Check for other problems there could be something more serious underway.
If your are unfamiliar with the inner workings of a Carver amp I would suggest sending it to a qualified service person that has working knowledge of Carvers.
Good luck.

[tiltedhalo]

Oh by the way , do you mean a bad triac or a 2n3055 2n2995 that are mounted on the back wall of the amp next to the inputs?? the two transistors are a descrete regulator designed to deliver +/- 15VDC to the meters and protection circuit.
I ask because triac faults are uncommon and most likley are signs of more serious problems or poor service work.

[jifop]

urm, sorry last post made no sense, there is a resistor burning out on one of the legs of the voltage regulator, i thought the reg may be dead?

it was then that i noticed the caps but could the dead caps cause problems?

carvers are a new beast to me in all honesty, the two large capasitors look fine externally. i am happy to work through it i have all the tools and i wouldn't know where to start with finding a carver repair agent.

[jifop]

thanks its actually r67 that is burned out

[tiltedhalo]

Could you post a couple pics??

[jifop]

i can do yes, i'll do them on monday!

thankyou so much for all your help so far, this really is a friendly forum who's members appear to have a wealth of knowledge!

[jifop]

right here we go, this is the amp as i got it, obviously it has had a new fan fitted and the cap mod done. all i have done to it is turn it on and bell out the diodes.

as i said when powered up R67 smokes like a goodun, i assumed this to be something related to the regulator, could that be caused by the caps?

anyway here are the pictures

Overall photo


Caps


Burnt resistor


So what should i do? where should i start? and what capasitors should i be buying? rs is my supplier of coice if possible