Marantz PM66SE Question

[dark0n3]

Hi,

Just got myself a Marantz PM66SE Amp, but both the speaker outputs are dead, and the fuse in the psu was blown.

Removed the output transistors and changed the fuse, now i get powerlight, but what else can be blown ?

I know i need to buy 2x 2SC3182 and 2x 2SA1265 to replace the bad transistors.

Some help would be nice, thanks in advance

Regards
Ronni

 

[dark0n3]

Update:

The relay dosent active when the amp is turned on, any idea on why ?

 

[tomahauk]

check transistors in driver stage and in VA stage

 

[dark0n3]

Got it, the driver fets are gone, what can i replace them with ?

Regards
Ronni

 

[tomahauk]

what is that fet ?

 

[dark0n3]

Hi.

Its a pair of:

2SB1353A and 2SD2033

 

[sixtek]

These aren't mosfets, but bipolar transistors.

2SB1353
http://www.rohm.com/products/databook/tr/pdf/2sb1353.pdf

2SD2033
Same specifications, but PNP.

Replacements:
2SB649 (npn) and 2SD669 (pnp)

If you can't get 649 and 669, then try the cheap and easly available MJE340/MJE350. But their Ft is only about 10MHz, and Co is higher than 2SB/2SD's 30pF.

 

[dark0n3]

Thanks

Got some new parts home and rebuild one of the channels, but it keeps burning out the output transistors, any ideas on what to check ?

Checked all the other transistors, and they are okay.

 

[tomahauk]

maybe the AN7026 is broken, unmont the broken output transisotrs, and check voltage on bases of drivers and predrivers transistors

http://www.tomahawk.elsat.net.pl/x.zip

this scheme should be similar to PM66SE, its PM6010

 

[dark0n3]

Hi

ya the AN7062 is dead, no signal on output.

Gotta replace that.

 

[Stuey]

I repaired a Marantz SR-50 using the same transistor pairs (blown) and in that it was the bias pots that were shorted, resulting in excess current. I replace them with 25 turn cermet trimmers with a 0.5w rating.

 

[dark0n3]

Checked the bias pots, they are working fine, changed all the transistors on the left channel, but when the news output transistors are fitted the fuse blows and kills the output transes..

Any ideas ?

 

[dark0n3]

UPDATE:

Replaced all the transistors and checked all the resistors, they are ok.

Im soon running out of ideas.

Regards
Ronni

 

[dark0n3]

On more update:

The Q704 and Q703 are getting very hot, is that normal ?

 

[dark0n3]

Anyone ?

Im out of ideas..

 

[tomahauk]

whats about AN7062 ? is it good ?

check voltage on bases of transistors after AN7062 output

 

[dark0n3]

Hi ya the AN7062 should be ok, changed it with a new.

The voltage on the bases is around 40 volt.

Regards
Ronni