4 replies to this topic

[CBDSonline]

Thanks to all for the help so far.

The Pontoon Club is about 90% salvaged now and i am on the final bend before she is done.

I have 10 lamps that i can't get to light up. They are not connected to the main lamps but to the triac (white) connector on the mpu4 board and i cant figure out what is - and + voltages and what they should be.

I dont know if the psu is crapping out or if its the board.

The board has had a bit of battery leakage but i think i have got it sorted. a pair of aa nicad batterys are in an external holder away from the mainboard now and she keeps the bank totals etc.
i had to replace 3 1r resistors that were corroded and everything seems ok apart from these 10 lapms.

I will try and put a diagram on of the pins i need measured on a known working mpu4 mod 2 board.


2 points are in red, 1 on the main psu connector and 1 on the triac connector(they are linked on the pcb by a track).
2 points in blue are on the triac connector

The 3 connections on the triac connector feed 2 lines of 5 lamps (which are brand new) but just refuse to light up.

On measuring i get about 0.2v + on the red connector on either triac pin or psu pin. and on blue pins 0v neither + or -

I would think the psu is crapping as half of the lamps that do light are flickering nice while the other half are ok with no flicker.

[skabaz]

not going to go into too much detail but i have had a fault on a barcrets mpu4 machine before with half the lamps flickering and the rest were ok and it was a power supply fault.

baz

[CanonMan]

not going to go into too much detail but i have had a fault on a barcrets mpu4 machine before with half the lamps flickering and the rest were ok and it was a power supply fault.

baz

I bet if you take the cover off the power supply you'll find that both bridge rectifiers are dry jointed, and possibly the capacitors too.

Seems very common to me and could well cure your problem if you remove the old solder, clean up and resolder them. If not, and the lights are still playing up, replace the two big capacitors.

Every time I buy a machine I always dismantle the PSU and resolder *all* the joints, as well as replacing anything that looks suspicious, and making sure the mains earth connection is good. So far, I haven't had a single PSU give up on me after the initial 'preventive maintenance'

[skabaz]

yeah i'm pretty sure it was the capacitors that had blown.


baz

[CBDSonline]

thanks guys. i will check the bridge recs and caps tomorrow
and let you know. A little bit of soldering rework never goes wrong in electronics. Just a shame switching atx psu's ain't as easy.