SST 01 Rev 1

[peranders]

Esprit wrote:

heaveno Folks very new to this forum


After two years of uninterrupted service, Relay K2 fails to latch.
When power is applied the points continuously bounce, is there a fix.

[peranders]

November 21, 2024, 06:36:30 PM
First of all (if possible) use a 24 V source with current limitation. It's much safer not having live voltage.


Connect 24 V across the DZ1 zener or similar point. Start with T3 and go backwards. What is the base-emitter voltage on T3? Should be 650 mV and the collector-emitter voltage less than 200 mV.

[peranders]

Esprit wrote:

November 29, 2024, 11:26:43 AM
Please accept my apologies for the delay in answering (I am waiting the return of my bench power supply)

[peranders]

December 02, 2024, 09:09:24 AM
No worries. Take your time.

[peranders]

Esprit wrote:

heaveno, I have two of the SST01 rev.1, one each in mono Pass F5t.
Following application of 24v across DZ1, the following results were obtained.


PCB No1
T3, B/E= 0v.    C/E= 22v
T2, B/E= 23v.   C/E= 23.1v
T1, B/E= 143mv. C/E= 40mv


PCB No2
T3, B/E= .94v.  C/E= 60mv
T2, B/E= .4v.   C/E= 22.2v
T1, B/E=.623v.  C/E= 1mv

[peranders]

T2 is suspect since you can't have more than 1 V across base-emitter.

[peranders]

T2 replaced on PCB 1, points on K2 continue to bounce.


D1,D2,D3,D4,and DZ1,all changed, K2 points continue to bounce.

Not Shure what to try next?.

Will please measure the voltages around T1 and T2 when you have 24 VDC connected across DZ1.

Try to measure the coil resistance of the K2 to rule out any shorts.

[peranders]

Espirit wrote

heaveno
Having difficulty entering the forum.
Please find message attached.
Hi
Board 1
T1
B-E= 143mv
E-C= 40mv
C-B= 0.0-0.6mv

T2
B-E= .4v
E-C= 22.6v
C-B= 0.0-0.6mv

Board 2
T1
B-E=.623mv
E-C= 22.2v
C-B= 1.8mv-6.6mv

T2
B-E= .4v
E-C= 22.2v
C-B= 0.0mv-2mv

Both coils changed

Regards
James

[peranders]

Both transistors are dead.

The 27 V zener should also be dead. Check if you have max 27 V across it if you have supply voltage applied. Make sure you have a current limitation otherwise you will fry it. You can also do a diode test. RED wire on anode (ground) and BLACK on cathode. You should get 0.6-0.7 V.