fitting a new lithium battery to an old original minelab sovereign

[Altra]

Hey Keith good going. Those voltages all look good. If you haven't tried it already, repeat the test with the coil connected.

[keith777]

Hey Keith good going. Those voltages all look good. If you haven't tried it already, repeat the test with the coil connected.

Hi again Altra

i got two different voltage results depending on how i did the tests.

if i connected the coil before switching on the machine. this is when the machine will just give a loud buzzing noise only and do nothing else. the voltage results are.
U24 TLO62 pins 4 and 8 give 11.05v
U24 pins 8 and 1 give 1.16v
U21 pins 11 and 4 give 7.33v

if i switch on the machine first. then connect the coil. this is when the machine will work ok. the voltage results are.
U24 TLO62 pins 4 and 8 give 11.32v
U24 pins 8 and 1 give 2.42v
U21 pins 11 and 4 give 9.84v

[Altra]

Do the test with the coil connected and powered off. Turn on and let it run see if Q6 or Q7 get warm. These transistor are the voltage regulators. If you have a second coil try that also to eliminate that as a problem

[keith777]

Do the test with the coil connected and powered off. Turn on and let it run see if Q6 or Q7 get warm. These transistor are the voltage regulators. If you have a second coil try that also to eliminate that as a problem

i left the machine off. then attached the coil. then i switched the machine on. i put my finger on the Q6 component for about 10 seconds. it was cool. then i put my finger on the Q7 component and it was red hot.
i unplugged the coil from the machine and the machine settled down with no constant buzzing sound. i checked the Q7 component again with my finger and it had cooled down. i plugged the coil back in whilst the machine was still on. the machine worked ok again as it does doing it this way. i checked the Q7 component again with my finger and it was cool.

so am i wright in saying that the Q7 component needs replacing.....

[Altra]

Well there are two possibilities. Q7 is bad or something on the -5V line is shorted. I think all the IC's are good since the voltages are ok without the coil . It's like the large electrolytics need to charge up before the coil is attached. Q6 could be bad causing Q7 to get hot. If it were my unit I would try replacing Q6 and Q7. Buy a few of each in case it's something else.

[keith777]

Well there are two possibilities. Q7 is bad or something on the -5V line is shorted. I think all the IC's are good since the voltages are ok without the coil . It's like the large electrolytics need to charge up before the coil is attached. Q6 could be bad causing Q7 to get hot. If it were my unit I would try replacing Q6 and Q7. Buy a few of each in case it's something else.

i bought this for a replacement for Q7 is Q6 the exact same? thanks again.......

https://www.ebay.co.uk/itm/132174102...Bk9SR_KWhN6FYQ

[Carl-NC]

No, Q6 is a PNP, BC856.

[keith777]

No, Q6 is a PNP, BC856.

H Carl.

the part Q6 on the board is the same shaped typed component etc as Q7 but when i look up for a PNP BC856 i just get a different type shaped transistor.



.

[Altra]

Carl is right that's a PNP. It looks like the BC856 is only made in surface mount currently. Believe it not that detector is 30 years old! You can probably use a 2N3906 or 2N2907 TO-92 package.

[keith777]

Carl is right that's a PNP. It looks like the BC856 is only made in surface mount currently. Believe it not that detector is 30 years old! You can probably use a 2N3906 or 2N2907 TO-92 package.

thanks again Alti. i so much appreciate it.........

[Carl-NC]

Can you read the part number printed on Q6? A 2N3906 should work but you want to make sure you get the pins correct.

[keith777]

Can you read the part number printed on Q6? A 2N3906 should work but you want to make sure you get the pins correct.

Hi Carl.

here is the Q6 component on the board.......

[kt315]

BC556
C B E
collector base emitter

[keith777]

BC556
C B E
collector base emitter

Hi Kt.

is this ok?

https://www.ebay.co.uk/itm/141432859374?hash=item20ee0e2aee:g:kDYAAOSwq7JULFZ U&amdata=enc%3AAQAHAAAA0BrorC84Rf1MvGE3a%2F4TX9tId hZq%2FaMCOs775IbvdR1YWPAS%2BIqlYSfHeEETtvxeRSrmbFK DcK3an3wL9%2BgXfbkcB0NrQ%2B%2BKcZHeKIg9RGx2WIzIRTX SybCIY7BNCEAlF5UfTBa3m6VCcillsIu882jFGHQXiflp%2Bpz 850uMEuO5j0U4CT2PFgnvWcs9kR3ljpQ1pY2NT6%2BFBc5uD9n ZSsFmrDHDP1JYIZDJCn0JHRTjMFKxKHY9ibayV7BgRm%2BAuGW TLH3VeZPs4pfBrB0qlFw%3D%7Ctkp%3ABk9SR4qA9tOGYQ

or

https://www.ebay.co.uk/itm/185141581...Bk9SR_KlnNSGYQ

[kt315]

you may take one from righ part of this table, but if you take one from middle part you have to REVERSE it, mirorred, on set.
you may not take one from left column.