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lohworm
Copper Member
France
27 Posts |
 Posted - 04/15/2009 : 18:56:55
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Hello !
I just got a PH-2...It's working when used with a power supply (PSA with daisy chain) but not when used with a 9V battery...
What are the components or connections to check first for the most frequent causes of this failure ?
Thanks
Laurent |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 04/16/2009 : 15:37:41
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Hi lohworm
Check the battery clip, sometimes the wires break.
Check DC input socket, it has a small metallic spring switch in it,
- It may be not working-corroded, or lost its spring tension.
- look inside the socket you will see it.
- when you remove the DC plug it switches over to battery power.
Other than that, please upload some internal pics of the pedal.
Someone may have tried to perform some mods on it?.
Regards Dr. Bob  |
Edited by - Dr. Bob on 04/16/2009 15:38:49 |
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lohworm
Copper Member
France
27 Posts |
Posted - 04/16/2009 : 16:20:36
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Hello and thank you for your very useful reply !
I've checked what's happening at the DC input socket when something is plugged or not, by comparison with a working OC-2...
Here are the results :
OC-2
with nothing plugged in the socket : 9V at both the two red wires, 0V at the blue one
with a DC jack plugged (but no power in) : 9V at the middle red wire, 0V at the outer red wire, about 0.3V at the blue wire (?)
So : something changes in the socket when plugging a DC cord
PH-2
with nothing plugged : 9V at the red middle wire, 0V at the outer red wire and at the blue wire
with a DC jack plugged : 9V at the red middle wire, 0V at the outer red wire, about 0.3V at the blue wire
So : nothing changes here, and the DC socket remains as if there is a DC cord plugged, even when there is not...
I've made other measurements with my ohm-meter, and it confirms a different behaviour between OC-2 and PH-2, when plugged or not, around the middle red wire...
next step : swap the DC sockets between th working OC-2 and the non working PH-2... |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 04/16/2009 : 16:48:05
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Hi lohworm
Good Tech Detective work.
It definitely sounds like the switch in the socket is staying open circuit.
If you look into the socket, you will see
a center metal pin, this is the (-) DC in
Then you will also see a folded flat piece of metal, this is the spring part of the switch. & it's the outer (+) contact on the DC plug, coming from your power supply.
When you pull out the plug, it should make contact with the the THIRD contact on the socket,
therefore switching the pedal over to battery power.
Sounds like the flat part is not making contact, with the third contact for some reason.
It might be just a build up of dirt-dust-slight corrosion.
Sometimes it get damaged from excessive current from a reversed power supply, but in that case, the protection diode is also fried.
It's a common & mostly overlook fault.
It's easier to look at two sockets with a meter - than it is to explain.
Good luck, sounds like she is going to be working again soon. 
Do you think you need a Schematic?
Regards Dr. Bob
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Edited by - Dr. Bob on 04/16/2009 16:55:28 |
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lohworm
Copper Member
France
27 Posts |
Posted - 04/16/2009 : 17:35:26
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Hello Again ! (Rick Ocasek tribute  )
I've swapped the DC socket and now I've a working PH-2 !!
(and a non-working OC-2  ...)
Have to find a replacement DC socket now...Do you know the "official" BOSS reference or serial for that part ?
Finally, I'll be pleased to get PH-2 schematics as I did not find it on the net.
Thanks for your help !
Regards.
Laurent |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 04/16/2009 : 17:45:37
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Hi lohworm
Great news.
You might want to try & clean the inner contact on the DC socket.
It works sometimes, it might just be dirt.
It's worth a try,
- you can find these on evilbay sometimes as well.
PM me - re the Sch.
Regards Dr. Bob |
Edited by - Dr. Bob on 04/16/2009 17:46:07 |
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Sray10
Silver Member
USA
150 Posts |
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lohworm
Copper Member
France
27 Posts |
Posted - 12/03/2009 : 18:00:28
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Hello, I'm back
This time I have a HM-3 that works well with PSU but with battery only if it's a totally new one, fully loaded with its 9V...
As soon as the available voltage is lower than, for example, 8.5V, it does not work anymore on battery...
I opened it and saw that a diode (the protection diode ? it's near the DC socket) has been replaced on the PCB...
If the diode is the wrong type, is it possible to get the observed behaviour ?
Does anybody knows what is the right model of the protection diode ?
regards,
Laurent |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 12/03/2009 : 22:38:22
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The actual part is a S5688G recifier diode, however, a common-garden 1N400x series diode will do the trick.
It sounds like maybe Q6 has some issues. If D9 is replaced, Q6 may have been damaged by the event that killed D9. Any small signal NPN transistor will work for Q6 (take care with lead orientation). |
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lohworm
Copper Member
France
27 Posts |
Posted - 12/03/2009 : 23:36:29
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OK, thanks Laurie...
And that transistor Q6 is not involved when working with PSU ? (I should learn to read schematics )
(I read 751 on the diode, maybe 1N751 ?) |
Edited by - lohworm on 12/03/2009 23:37:20 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 12/04/2009 : 00:15:34
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quote:
Originally posted by lohworm
OK, thanks Laurie...
And that transistor Q6 is not involved when working with PSU ? (I should learn to read schematics )
(I read 751 on the diode, maybe 1N751 ?)
Q6 is used all the time... but if it is damaged, it might not handle the lower voltage of a dying battery. Just a theory at the moment. Only way to tell if Q6 is OK is to pull it and use a transistor/diode tester on it.
Not sure about the "751"... a 1N751 is a 5.1V Zener diode - definitely not what you want for D9. |
Edited by - Laurie on 12/04/2009 00:18:08 |
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Topic |
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what to check first when PSU:OK / battery:fail ?
