Meridian 103 - bdy56 Transistor Alternatives?

[Thomo]

Hi. I have an old Meridian 103 which has four BDY56 as output transistors. Unfortunately two of these are bad and the only replacements I can find are £12 each.

Could I use any of these instead?

mj21194

2n3773

bdy56

Any help greatly appreciated, thanks.

Lee

 

[poynton]

Can't you use the plastic TO220 versions ?
A lot cheaper.

 

[Thomo]

Hi Andy. I don't think that it would be possible to mount them on the heatsink. They're mounted in a similar way to a Quad 405.

I have stuck the 2n3773's in just to see if they work but I have a problem with one channel. I don't have a scope so I can't check for oscillations etc though. Any ideas as to whether they're suitable? They seem to have very similar specs looking at the datasheets, but then I am a bit of a noob.

Lee.

 

[burbeck]

hi Lee,
have a look at
BUV20
MJ15003

 

[Thomo]

Hi Bob. Thanks for that. Do you think that the mj15003 will have as good a sound as the originals? I have them in my Quad 405 but I am told they're not as good as the 2n3773's.

Lee.

 

[burbeck]

hi Lee,
the MJ15003 are nice and cheap try them out.
the BUV20 are better but expensive.

why not give meridian service a call and ask there advice on the sub of these?
i repaired one of these amps a while ago which had one set of output devices already replaced (by meridian) for the life of me i cant remember the type number they used, it may have been BDY95 not sure. i was only replacing the speaker sockets.

let me know if you do call them

 

[Thomo]

I rang them yesterday, and they told me that they would be ringing back today, as they guy I need to speak to wasn't there. Aparently he worked there when the 103's were in production!

Meridian customer service has been outstanding I must say. How many companies would go out of their way to provide service information and help about a product they marketed nearly thirty years ago?

Lee.

 

[burbeck]

hi Lee,
i agree meridian are one of the few companies left with great back up.

 

[burbeck]

hi Lee
did you get an answer from them?

 

[Thomo]

Not yet, I will have to try again I think. Whilst waiting for a reply I ordered four MJ21194G transistors. I got them for $15 shipping which works out at around £7.50. Not bad I thought.

In the mean time, I fitted 2n3773's but I still have no joy at getting the thing to work. How accurately can you tell a transistor is faulty by testing? I have a fairly standard multimeter and used the diode test function.

I removed all the transistors and tested them, they all seemed ok, so I put them back with the new output trannies and still read -1.2v & -2.3v offset. I'm thinking of sending it to Meridian but don't want to, as I wouldn't learn anything out of it.

Lee.

 

[burbeck]

hi Lee
the diode test function is a very basic test for bjt's, sort of a go no go test. it does not test leakage or gain.

also be careful when checking. b, c and b,e diode check, should give you a diode drop (0.5 to 0.7v) reading on each,

but if the transistor is short from c,e it will possibly pass this test.
test from c,e as well, no reading is good.

are both channels of this amp faulty?

 

[Thomo]

Unfortunately, yes both channels. I think I'll order a complete new set of transistors and just replace the lot. They're cheap and this seems like the most reliable way of fixing it.

My Multimeter has a Transistor test socket, but I don't know what the readings mean. Any ideas?

Lee.