MTC9110 issues

[Yakama]

I’ve been working on the MTC9110 chassis’ from the neo geo’s and they both had vertical sync issues. R38 was faulty on both and that has fixed the sync issue on one of them but I can’t seem to adjust the width on this one. One side is always out of picture. Going from Google I have checked B+ and it seems way too highly at 181.5v at the pin where the black wire link in the scan coil/yoke plugs in but strangely only like 21v at TP1. I tested C42 and it was ok, C41 seems to be testing a bit low at about 10.44nf and I believe it should be 12nf, is this ok or too low?

Chassis had all electrolytic caps changed apart from the large filter cap so C38, which Google also suggested, has already been changed. It also suggests c37 but I haven’t removed it as it seems to have another cap soldered to the same pads on the bottom of the board too?

I’ve reflowed anything that looked suspicious. Also the voltage regulator tested ok out of circuit but I’ve one on the way just in case.


The second chassis still won’t sync but I notice that it also has B+ of 181.5 at the pin where the black wire link in the scan coil/yoke plugs in but nothing at TP1?

This one hasn’t been recapped the voltage regulator tested ok out of circuit, ive not taken anything else out yet to check as was working on the other chassis first. This was the chassis that I posted a pic of before that had the remote boards smashed and cracks in the main board but I’ve patched them

 

[mawrick]

I’ve been working on the MTC9110 chassis’ from the neo geo’s and they both had vertical sync issues. R38 was faulty on both and that has fixed the sync issue on one of them but I can’t seem to adjust the width on this one. One side is always out of picture. Going from Google I have checked B+ and it seems way too highly at 181.5v at the pin where the black wire link in the scan coil/yoke plugs in but strangely only like 21v at TP1. I tested C42 and it was ok, C41 seems to be testing a bit low at about 10.44nf and I believe it should be 12nf, is this ok or too low?

Chassis had all electrolytic caps changed apart from the large filter cap so C38, which Google also suggested, has already been changed. It also suggests c37 but I haven’t removed it as it seems to have another cap soldered to the same pads on the bottom of the board too?

I’ve reflowed anything that looked suspicious. Also the voltage regulator tested ok out of circuit but I’ve one on the way just in case.


The second chassis still won’t sync but I notice that it also has B+ of 181.5 at the pin where the black wire link in the scan coil/yoke plugs in but nothing at TP1?

This one hasn’t been recapped the voltage regulator tested ok out of circuit, ive not taken anything else out yet to check as was working on the other chassis first. This was the chassis that I posted a pic of before that had the remote boards smashed and cracks in the main board but I’ve patched them

Not sure if this is relevant but seeing you have some problem with the remote board, just be aware that the remote board can cause width problems, I had a chasis with problems with the width turned out it was caused by a short on the remote board so do check that board out:

Thread: MTC-9110 Width Problem

 

[Yakama]

Thanks, the width issue isn’t the one with the smashed remote. That’s the other one but I can’t get that one to sync yet even after replacing r38

 

[Flyback2021]

Crikey , sounds like both Chassis have needed a lot of work . Is there anything else you need or was missing from these cabinets that I can help you with ?

 

[Yakama]

Yeah they have been a bit of work to even get an image so far but I feel I am getting there. They both still have issues though with the B+ being so high but I don’t really know what I’m doing lol so im trying to learn as I go. I managed to patch up the broken one so I think I don’t need anything just now other than waiting on the parts I’ve ordered to try replacing bits.

 

[gunblade]

where are you reading the b+, i use one of the centre pins of the yoke connector

 

[Yakama]

Yeah that’s where I was reading it at plus at TP1 but getting different readings as mentioned above

 

[gunblade]

black probe on the frame and red probe one of the centre two pins?
181v should shut down the chassis

 

[Yakama]

Yes that’s how I measured it, I will double check it again then

 

[Yakama]

Ok I’m back to no image on the first chassis mentioned now 🙈 this is the b+ reading

 

[Yakama]

This is the second chassis that was smashed up but wont sync and again b+

 

[Yakama]

You can see there is text on this second chasssis but I just can’t get it to sync

 

[gunblade]

yoke has to be plugged into the impedance matching pcb and the connector from that has to be plugged into the main chassis

as for sync issue, first check sync switch in correct position, then check the 4 sync transistors - TR10 to TR13, then IC2

 

[Yakama]

Ah my mistake I thought you could read that disconnected

IC2 is ok as I swapped that for a new one and no change. And sync switch is in correct position. Will check the transistors. Thanks

 

[gunblade]

is the chassis shutting down?
do you have an eht probe?

 

[Yakama]

No. Now I have read b+ correctly I get 127.3v on the one I had managed to get sync on but is now not showing anything and 123.4v on the one that is showing an image but not syncing

 

[gunblade]

voltage low on these is normally an issue with resistor in regulation circuit
glass diodes on these chassis corrode, in particular under the fan area
important to have correct tools, eht probe to read hv, focus and screen volts. bench meter to read heater voltage

 

[Yakama]

Am I ok testing the transistors in circuit or should I remove them? Sorry for the boob questions and thanks for the help

 

[Yakama]

Yeah sadly I don’t have an eht probe just my multimeter. I will have a look at those resistors

 

[gunblade]

problem with small signal transistors is they go leaky and fail under load so very difficult to prove, if i get sync issues and suspect transistor then i replace all of them for new - watch out though as there are bc548 and bc558 - you get same issue on the colour circuits as well
the resistors i would be looking at R113,114,115,118. R110 was an issue on early model but they changed to metal oxide higher wattage and that sorted it - in any case that caused very low b+
I press a screwdriver blade against all glass diodes to make sure they are intact

If you intend fixing more chassis then please get an eht probe for your own safety, its critical to know what the hv is doing