Hantarex MTC 9110 – Low B+ (~122V), slight shimmer, green tint

[lagunasunrise]

Hi all,

I’m working on a Hantarex MTC 9110 chassis that I have fully recapped, and I’m trying to track down a few remaining issues.

Some background: when I first got the arcade machine, the monitor worked briefly, but then suddenly went dead. I later found two burnt resistors on the chassis. I replaced those resistors, repaired the damaged PCB area, and also checked/replaced nearby components as needed before doing a full recap.

The monitor is now working again, but I’m seeing the following issues:

- B+ measures around 122V (I believe it should be ~130V)
- The picture has a slight shimmer/jitter (not very noticeable, but visible on close inspection)
- There is a green tint in the image, even with the green cutoff/level on the neck board adjusted all the way down

Unfortunately I didn’t pay attention to the colour balance when it was briefly working before the failure, so I’m not sure if the green tint was already present or not.

So far:

- Full electrolytic recap done
- Burnt resistors replaced and PCB repaired
- Nearby components around the damaged area checked/replaced
- Basic visual inspection and some solder joints reflowed

My questions:

1. Is ~122V B+ within a reasonable range for an MTC 9110, or should I suspect an underlying fault?
2. Could the slightly low B+ be responsible for the subtle shimmer?
3. For the green tint: is this more likely to be a CRT issue (green gun emission), or should I focus on the RGB driver circuitry on the neck board?

Any advice on what to check next would
be much appreciated.

Thanks!

 

[mawrick]

Hi all,

I’m working on a Hantarex MTC 9110 chassis that I have fully recapped, and I’m trying to track down a few remaining issues.

Some background: when I first got the arcade machine, the monitor worked briefly, but then suddenly went dead. I later found two burnt resistors on the chassis. I replaced those resistors, repaired the damaged PCB area, and also checked/replaced nearby components as needed before doing a full recap.

The monitor is now working again, but I’m seeing the following issues:

- B+ measures around 122V (I believe it should be ~130V)
- The picture has a slight shimmer/jitter (not very noticeable, but visible on close inspection)
- There is a green tint in the image, even with the green cutoff/level on the neck board adjusted all the way down

Unfortunately I didn’t pay attention to the colour balance when it was briefly working before the failure, so I’m not sure if the green tint was already present or not.

So far:

- Full electrolytic recap done
- Burnt resistors replaced and PCB repaired
- Nearby components around the damaged area checked/replaced
- Basic visual inspection and some solder joints reflowed

My questions:

1. Is ~122V B+ within a reasonable range for an MTC 9110, or should I suspect an underlying fault?
2. Could the slightly low B+ be responsible for the subtle shimmer?
3. For the green tint: is this more likely to be a CRT issue (green gun emission), or should I focus on the RGB driver circuitry on the neck board?

Any advice on what to check next would
be much appreciated.

Thanks!

Working on the same chasis at the moment.
what PSU are you powering with, I have a Hantarex US250 psu which have been recapped etc, but noticed the B+ (at TP10) showed around 123V, but when I power it with a 110V step down (AC) it does infact show 131V at the TP10 so seem like this voltage can vary quite a bit (my US250 put out apx 135V DC when no load is attached).
I have some additional problems so not really sure your 122V is to low or not but might be a thing to look into how the monitor is powered

 

[lagunasunrise]

Working on the same chasis at the moment.
what PSU are you powering with, I have a Hantarex US250 psu which have been recapped etc, but noticed the B+ (at TP10) showed around 123V, but when I power it with a 110V step down (AC) it does infact show 131V at the TP10 so seem like this voltage can vary quite a bit (my US250 put out apx 135V DC when no load is attached).
I have some additional problems so not really sure your 122V is to low or not but might be a thing to look into how the monitor is powered

Thanks, that’s really interesting.

I’m actually using the same Hantarex US250 PSU, and it has also been recapped. I did measure the voltage it outputs to the monitor under load at some point, but I don’t remember the exact value — it was definitely lower than the specified ~135V DC though.

I also have another machine with an MTC 9000 chassis and a similar US250 PSU, both still unrecapped. I measured that one as well, and if I remember correctly it was giving over 140V.

I’ll try swapping that other PSU into this setup and see if it has any effect on the B+ and the shimmer.

Thanks for the tip!

 

[tb2000]

You can have a varied input voltage but it should be 128v +10 or -20%, for example it will work from a WG transformer that puts out 120v. The B+ though should always be 130v and shouldn't really vary by more than a volt or two (maybe three) while the monitor's working - it will always change a little when the game image changes from light to dark screens and vice-versa - if it is too low like 122v then it will be changing the other voltages which come from the lopt. Check R110, it should be 33k. I'm assuming you've checked the TIPL762 voltage regulator? If it's bad it won't be regulating properly, you can swap in BU508A (same as the HOT) to check if it's not doing its job. For the green tint, check that your degauss ptc is working and that it's not stuck on - if it's stuck on you can check by simply pulling the degaussing ring from the socket. You might have a bad transistor (BF459) on the neckboard in the green circuit. You can prove that by swapping the green with either the blue or red transistors. If it's not that it could be one of the small signal transistors in the green section of the chassis (unlikely a resistor, could be a leaky diode, but also unlikely). For the jitter, is your jamma psu grounded properly? You may need to put a wire from ground to FG (field ground).

 

[lagunasunrise]

Thanks a lot for the detailed reply, really helpful.

R110 was actually one of the resistors that I’ve already replaced during the repair, so it should be 33k now.

I haven’t checked the TIPL762 yet. I’m actually about to place a Digi-Key order for some other projects, so I can add a BU508A and try swapping it in to see if the regulator might be the issue.

I’ll check the degauss PTC next and see if it might be stuck on. If that looks OK, I’ll try swapping the BF459 from the green channel with one from red or blue to see if the fault follows.

I’ll probably order a few BF459s anyway, but I noticed that some of the closest matching parts aren’t available from Digi-Key. Do you happen to know what would be a good, commonly available modern substitute for BF459?

As for the PSU, I’m using a US250 and it should be properly grounded, as it’s the only PSU in the machine.

Thanks again for the great advice!

 

[qjuk]

Also, shimmering could be due to the AC line filter.

 

[tb2000]

I've never really had to find a substitute for BF459 as I have some in stock and also have plenty of spares chassis with them on. With that said, you can get them from eBay no problem but I think the last ones I got came from Cricklewood Electronics. They have them for £2.70 each inc. vat. BF859 (as used on the Hanty Polo chassis neckboard) might work in place of a BF459 but i'm not 100% on that. They're both NPN transistors and they're pinned in the same order (emitter-collector-base) so they might work ok. You'd possibly have to put a small heatsink on a BF859 though like they have on the Polo chassis.

 

[lagunasunrise]

Thanks again for the suggestions.

I’ve now done a few more tests:
- Checked the degauss PTC (also tried disconnecting it) no change
- Swapped the green channel BF459 with the blue channel – no effect, the issue stayed on green
- Also tested without the game PCB connected

The green tint is mainly visible in dark areas — blacks look slightly green — but it’s not really noticeable in white or other brighter colours.

 

[lagunasunrise]

I did another test and disconnected the green video signal wire going from the main chassis board to the neck board.

Even with the green signal disconnected, the blacks still have the same slight green tint.

Does this now point quite strongly towards the CRT itself (green gun not fully cutting off), or is there still something else worth checking?

Thanks again for all the help.