2216 PA clamp diodes?

D

dorke

Member

• Feb 16, 2014

• #1

Hello,
I'm trying to fix a Marantz 2216 receiver.

Both PA channel are dead with power transistors shorted out(all directions)
One driver transistor and the biasing transistor also bad on both channels.

There are 4 clamping diodes(2 per channel) on the board marked (H715-H718)'
their color is red+green cathode mark (they are actually soldered on with no dedicated pads on the board) .

The diodes are marked as "usual" diodes on the schematics.
I couldn't find them in the parts list( board P700).
The diodes also look bad.
Anyone knows the diodes part number?
Thanks

 

patfont

AK Subscriber

Subscriber

• Feb 16, 2014

• #2

1n60=BAT41

 

Robisme

Sansui Enthusiast

• Feb 16, 2014

• #3

Check the schematic. It should list them.

Rob

 

D

dorke

Member

• Feb 17, 2014

• #4

I cheked,they are not listed

Only the transistors are listed in the schematics.

 

D

dorke

Member

• Feb 19, 2014

• #5

Photo+schematics any idea?

The diodes are marked with arrows on the photo and schematics.
Any Idea wht is the part number of the diodes?
Could anyone suggest a suitable replacement in that circuit.
Thanks

 

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patfont

AK Subscriber

Subscriber

• Feb 19, 2014

• #6

Did you happen to read post #2:scratch2:

dorke said:

The diodes are marked with arrows on the photo and schematics.
Any Idea wht is the part number of the diodes?
Could anyone suggest a suitable replacement in that circuit.
Thanks

Click to expand...

 

D

dorke

Member

• Feb 19, 2014

• #7

@patfont
No I missed it.
Where those the info come from,Are you sure?
Thanks

 

patfont

AK Subscriber

Subscriber

• Feb 19, 2014

• #8

Look at the 2215 on the AK Database, they are also used there, same place.

 

D

dorke

Member

• Feb 19, 2014

• #9

Thinking about the distructive chian of events

The PA on my 2216 has gone a dramatic destructive event.
I don't quite understand what happened and how that chain of events started.
I'm thinking those diodes are not "strong enough" for the task as all 4 of them are blown up(not conducting).
I think to change the diodes to something with greater reverse voltage breakdown and greater current capability.
Note that, The supply voltage to the final pair is 53V to 0.
Can you suggest one?

On my model there is no fuse protection on the Speakers outputs.
Thinking to add one as well.
Any thoughts?

Thanks

 

patfont

AK Subscriber

Subscriber

• Feb 20, 2014

• #10

the real question is what caused all 4 of them diodes to go.





QUOTE=dorke;7579361]The PA on my 2216 has gone a dramatic destructive event.
I don't quite understand what happened and how that chain of events started.
I'm thinking those diodes are not "strong enough" for the task as all 4 of them are blown up(not conducting).
I think to change the diodes to something with greater reverse voltage breakdown and greater current capability.
Note that, The supply voltage to the final pair is 53V to 0.
Can you suggest one?

On my model there is no fuse protection on the Speakers outputs.
Thinking to add one as well.
Any thoughts?

Thanks[/QUOTE]

 

D

dorke

Member

• Feb 23, 2014

• #11

Agree,I don't know the cause.

I'm thinking to replace the
1N60 (Germanium 40V/30mA)
with a "stronger" 1N4148 (Silicon 75V/150ma)-the break down voltage is 100V peak.
Only draw back is giving up 0.5V(max) of clamp voltage which I think is fine.

The 1N4148 are very cheap 50 pcs. sell for 1$ on Ebay.

Any thoughts?
Thanks

 

sregor

AK Subscriber

Subscriber

• Feb 23, 2014

• #12

I'm confused. I don't think those are 1n60 or germanium. Standard practice is 1n4002 or equivalent for flyback diodes. They are there only to prevent reversed voltages across the output transistors. (thats why they are connected "backwards") and don't need to be anything special.

 

sregor

AK Subscriber

Subscriber

• Feb 23, 2014

• #13

2216b manual show W06B which are ordinary rectifiers. Also rare that diodes fail open.

 

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ChrisMarantz

Super Member

• Feb 23, 2014

• #14

W06B are silicone diodes, according to one of my interchange manuals, 1N4007 are the correct replacements.

 

Attachments

• DSA1203000-80.pdf

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D

dorke

Member

• Feb 24, 2014

• #15

Clamp diodes need to be fast enough to handle the impulse expected.

What is the impulse voltage in this case?
It should be the L x di/dt of the current trough the coil at the output of the PA.
The impulse could be quite large if someone disconnects the speaker while the PA is at full volume,isn't that so?