Hantarex Polo 25 - keeps blowing fuses.

[sevenleaf]

I have just started working on my Sega Rally Upright. When I bought it there were no signs of life but I now have it playing blind.

It does, however, keep on blowing fuses, the instant the machine is turned on. I was told this when I bought it but as it's the age old lie when selling something ("probably just the fuse or something, easy fix mate") I paid little notice. The fuse I found in there was a 6.3A fuse and it's only supposed to have a 3.15A.

I found the degausing lead unplugged too (which ties up with Randy's diagram) and it was fixed (pretty badly, many repaired lifted tracks and repairs) a year ago according to the sticker.



1. FETT101 - is this the fuse holder? With Fluke on buzzer there is no circuit between either fuse holding clip and metal chassis case.

2. There is no buzz between any diode leg and chassis case.

3. I have no C101-C103 and C104 is not shorted (checking legs to chassis).

4. Degaussing coil not shorted to frame.

I have no idea where to check from here. Any ideas?

All of my electronics is frm GCSE physics at school and self taught from there on so if reading the above I'm not checking correctly then please do let me know!

Edited to update link to randy's flow diagram...

[grantspain]

remove the ptc component and then try

[sevenleaf]

Thanks Grant, will try that next weekend and let you know how it goes. You are single-handedly fixing my collection at the moment

If it works without the PTC in the circuit does that mean that replacing the part will fix the problem? I have just had a look and can get a couple of direct replacements for under a fiver.

[grantspain]

Thanks Grant, will try that next weekend and let you know how it goes. You are single-handedly fixing my collection at the moment

If it works without the PTC in the circuit does that mean that replacing the part will fix the problem? I have just had a look and can get a couple of direct replacements for under a fiver.

ah jeez i better start charging then

[sevenleaf]

remove the ptc component and then try

I'm going to be trying this tomorrow. When I fire it up without the ptc do I leave J102 (degauss) unplugged?

I'm really hoping it works as I have wanted Sega Rally for nearly 15 years!

[SirPeale]

Degauss can be unplugged, but I don't think that's your issue.

FETT101 isn't your fuse holder.  It's an IC, likely with a heatsink. 

Do you have the schematics?

[sevenleaf]

I have just gone over the schems again and found T101! I was looking for FETT101 . I thought it was strange as I've only seen IC, C, D, R, T etc before, not FETT! DOH.

The part is IRFBC30 and I can get hold of them easily enough, pain to get to on the board though!

If there are any other parts you feel could be the culprit, please do say. My supplier sells the components at a very reasonable price but p&p is expensive in comparison on small orders so it's worthwhile me taking a gamble and buying loads of stuff.

EDIT: I've just tested T101's legs against the heatsink it's attached to and all 3 make a connection to it - 2 of the legs produce a solid tone from the Fluke and the other produces a single beep and a reading of 0.428

The part T101 in the machine has the following written on it: W0K948 P5NB60 - is the IRFBC30 written on the schematics a suitable replacement?

[sevenleaf]

I've replaced T101 with an IRFBC30 and removed the PTC. No change - still blows the fuse instantly.

Will the Polo chassis from my Ridge Racer (33") work on place of the 25"? The last thing I need is that to blow too!

[sevenleaf]

Have watched the first 2 of Randy Fromm's CRT tutorials on Youtube and am going to re-open this previously closed case.

Having re-read what I wrote back in 2009, I think that testing the capacitors from each leg to the chassis was not the correct method of deciding whether the component had shorted out (back in 2009, I interpreted it as meaning to test if the component had shorted to ground, now I realise it probably means to see if the component has internally shorted).

So, hopefully by testing and replacing C101-104 I can finally get this cab working!

[grantspain]

check all the diodes in the primary psu section mate

[sevenleaf]

I'd forgotten that I had another med res Polo. The CRT came with the fuse blowing chassis has a suspected cracked neck, so I'm also going to try and fix the other one that has the good accompanying tube.

It's very red and has retrace lines. I guess I need to turn down the voltage on the LOPT?

[grantspain]

red drive tranisitor or red background too high

[sevenleaf]

red drive tranisitor or red background too high

Thanks mate. Changed both transistors and the capacitor (on the red path) that Randy suggests and its now all turned green! Will change the rest of them next weekend.

Also the lopt is already turned down as low as it will go...

[grantspain]

you need to change a few other caps,4.7uf 250v on the neck card will be a good start-also there are a couple of 100uf 250v and a 47uf 250v (c14,c177,c168)

[sevenleaf]

check all the diodes in the primary psu section mate

Meanwhile, back to the fuse blowing polo.

FET T101 - replaced with IRFBC30.
Replaced all 4 bridge rectifier diodes.
Changed PTC
Unplugged degausser
Tested C104 - tested with DMM and it's not shorted. May just replace it anyway. No C101-103 to replace.

The chassis has been mended a bit in places so I'm wondering if it's maybe not componenet failure.

[grantspain]

something is shorting straight to earth,ic101 is possible and r103-which i think is a ntc

[sevenleaf]

something is shorting straight to earth,ic101 is possible and r103-which i think is a ntc

Changed IC101, still blows the fuse. R104 is NTC10 but I can't find a replacement one online

you need to change a few other caps,4.7uf 250v on the neck card will be a good start-also there are a couple of 100uf 250v and a 47uf 250v (c14,c177,c168)

I changed T2,4,6, T3,5,7, C1,2,3 and IC1 (yet to order the ones you said) and got the best picture yet. The picture was bent in on the edges and the blacks and whites were displaying wrong so I adjusted the pincushion board, turned down the R and B pots on the neck PCB and turned up the screen voltage on the LOPT.

Do you think it could do with a whole cap kit or just the ones you mentioned above? Or just setting up properly (the tube and chassis didn't come together you see)?

[grantspain]

just looks like green overdriving to me

[sevenleaf]

There's no green pot on the neck board, do I just have to balance it with the r and b?

[grantspain]

there will be a green cut off pot-you should have 3 colour cut offs and 2 colour gains on the neck card