Sega G-loc deluxe motor power supply

[gc339]

It's rather strange these two resistors were cut at the same time.
They are only involved each time the power is switched ON just to limit current through capacitors C8 & C9, they are then short-circuited by TR1 in established and steady operation.

The plausible explanation is that TR1 cut itself first, so they had to undergo all the load to finally burn themselves.

[perjmolsen]

Hi

Yes its strange, but i think you explanation is corect  - its so exiting to get the new resistors and mount them 
I have ordered them in UK this time, so hopefully i get them at the end of next week.

If i had placed an order in china i'll have to wait a month before i get them and the diffrence where that i coud get 15 resistores instad of 5 for the same price - but i only need 2 for this project.

(I have two more powersupplys for the g-loc who also are dead, but i only need this one to work them i have two working for my G-loc)

Kind regards
Per

[gc339]

When I must order from a Chinese seller, I prefer those based in Hong-Kong rather than mainland China because the items usually arrive home in less than two weeks.

[perjmolsen]

Hi and good evening..

So now finally the new transistors for R1 and R2 arrived.
I have soldered them in, now i got 320 DC Volt  a step in the right direction at last .



BUT still no 12V or 5V present... dammit! 

Have i overlooked something...?
- Must i de-solder the L2 transformer one more time and test it now i have fixed my tester.. or is there some other component.

HELP!

[gc339]

Here is the schematic of the low voltage power supply :

Q1 & L2 are the main parts of a blocking oscillator :

• Winding 3-4 is the main primary winding of L2.
• Winding 1-6 is the feedback winding, used to drive Q1 gate and make it oscillate.
• Q2 is used to protect Q1 against :
  • Driving overvoltage (ZD2).
  • Drain/source overcurrent (R24 voltage).
• Windings 3-5, 7-8, 10-11, 12-13 and F-S are secondary windings, used to produce the low-voltage auxiliary DC supplies.
• The stability of the low-voltage auxiliary supplies is tributary of the +12 volts supply regulation provided via the DC feedback loop (optocoupler PC1 & shunt regulator IC3).

So, it's necessary to first check involved components in the blocking oscillator : transistors (Q1 &Q2), diodes (D4 ... D6, ZD1 & ZD2), resistors, capacitors...

[perjmolsen]

Hi GC339

Sorry for the late answer to your post.

I do not know if it helps, I have tried to measure if there is any volt present at the input of the L2 transformer. (I guess that's the input)

I have messured 0V at the two marked test points below at the back at the PCB.




And so far i have tested:
Q1 = Checks OK
Q2 = Checks OK
D4 = Checks OK (0.470 ohm one way and OL other way)

[gc339]

I have tried to measure if there is any volt present at the input of the L2 transformer.

To check voltage at the primary of L2, it's better to measure it between one of the two lite-blue surrounded points and one leg of R4. (are you sure R4 is OK?)

It's possible the DC/DC converter can't start due to a short circuit or an overload in an auxiliary supply. This possibility can be eliminated by desoldering one leg of diodes D1, D3, D9 and D10 (D8 must remain in place because the +12 volts is mandatory for voltage control to work).

[perjmolsen]

HI 

Regarding the R4 - i previously have replaced it with a new resistor, so i shroud be OK - but ill de-solder it and test it, just to be sure

I'll also try to test test input of the L2 by leg of R4 and one of the blue marked points and let you know what reading i get.

And also try the de-solder one leg of D1,D3,D9 and D10. to see if thats give me 12V

Thanks again

[gc339]

To check voltage at the primary of L2, it's better to measure it between one of the two lite-blue surrounded points and one leg of R4. (are you sure R4 is OK?)

Sorry, I was not careful enough and I made a mistake, it's R24 and not R4. So you must read :

To check voltage at the primary of L2, it's better to measure it between one of the two lite-blue surrounded points and one leg of R24 (are you sure R24 is OK?)

[perjmolsen]

HI

OK, thats funny.. when i looked at the items i had changed.. I looked at R24 and not R4, and where also planning to check R24
But anyway.. ill check it, thanks for the update

[perjmolsen]

Hi GC339

Just a quick update

I have measured between R24 and both of the blue circled test-points.
I have 328V in to the L2 transformer.


I have to go to work early tomorrow,so no more testing tonight...but tomorow i will test R24 and de solder one leg of D1,D3,D9 and D10. to see if thats give me 12V

[gc339]

Can you try with the other leg of R24 ?

[perjmolsen]

HI

I just tested with the other leg of R24 - also 328V present at both the blue circled marked test points.
Then the R24 might be good? it is also brand new

I have to try out the de soldering of one leg of D1,D3,D9 and D10. to see if thats give me 12V - then take it from there i guess..

Kind Regards

[gc339]

I just tested with the other leg of R24 - also 328V present at both the blue circled marked test points.
Then the R24 might be good? it is also brand new

With this last measurement I am quite sure R24 is OK.

[perjmolsen]

Hi

Just a quick question, regarding the de soldering..

The D1 diode, thats the bridge rectifier, are you sure that one of them i need to de-solder? if i de-solder one leg, will i not loose the power? i case witch leg?

I have de-soldered the following diodes at tested them in the china tester
D9 Tests as diode uf=575mv c=12pf
D10 Tests as diode uf= 580mv c= 11pf
D3 Tests as diode uf=585mv c=15pf

With the D9,D10 and D3 de solder still no 12V at fan outlet - but i gess that might be due to D1.. but i am not sure witch leg to de solder.

[gc339]

Sorry again, I forgot to postpone the second digit "1" when I drew the draft of the DC/DC converter (summer 2013), so it's  D11  and not D1