urgent help with baxi 105e needed please

[tiggerpussy]

Hi its cold up here in Scotland so your help would be gratefully appreciated.
My baxi 105e developed a problem on christmas day with a ch failure although the hw is fine, had been having an intermittent fault with timer
so suspected that first, no apparent fault ? (but shall be replaced) As control box was dismantled checked out pcb and components. Found resistor r23 to be blown and cannot source this 250k resistor locally until well into the new year. This effectively means that the ch is switched off.
Question is before I fork out over £100 for a pcb and timer can anyone suggest other than a fault with the timer why this resistor should fail?
as I dont want to fit a pcb only for it to fail instantly.

merry christmas and a happy new year to you all.

 

[ChrisR]

WHich board is it?
(5112380 or the earlier one which I think was 248074?)
I know a relay fails on the old board, wasn't aware of a lone resistor.

 

[Agile]

Dont expect that just replacing that resistor will fix the problem.

The resistor will have failed as a result of another fault.

Can you tell me how many potentiometers you have on your board? Do you have P3 and P4 as well as P1 and P2?

If I could look at your board I might be able to suggest what might have failed.

 

[tiggerpussy]

Hi, thanks for getting back to me so soon,
the board has three pots p1, p2, and p3, I also assume the sticker and barcode are the part no, which is 0.580.001(07)

 

[ChrisR]

It's a megohm on the current boards. Sure you haven't read the resistor backwards?
Appears to part of HT circuit so I don't see why it should only affect CH.

Have you checked that the switch on the diverter valve isn't waterlogged?!

 

[tiggerpussy]

Hi
Thanks again for your reply but I'm positive I have read the resistor correctly being being red green yellow with a gold tolerance, the exact same resistor is used at r57, however if i follow the circuit back it leads to pin two on the block connector from the timer (that would be the feed to the board from the timer).
I suspect that as mentioned in my first post a faulty timer (poss dirty, burnt, high resistance??) but intermittent fault i.e would not switch off at "O" sometimes would not switch on at "I"
this resistor being blown is acting like an open switch preventing supply to pt4 and beyond(as it appears sorry dont have a wiring diagram so trying to work through circuit logically and with HUGE MAGNIFYING GLASS as eyesight failing.
Just dont want to replace the board to find an NTC or other component etc is a culprit for blowing boards.
thanks again.

 

[Agile]

We need to know which PCB you have. They are not all the same!

On the 5112380 as Chris says its a 1 M resistor which is a static discharge leak between mains neutral and boiler chassis.

I am not convinced that we are thinking of the same PCB although this does have the three pots. It has CE number of 0051 BP 2783.

If the resistor is "blown" then how can you read the value?

250k is NOT a standard resistor value !!!

Tony

 

[tiggerpussy]

Thanks for your help
the other numbers on the pcb read as follows
CE PIN 0085BL0059 0118
565495.1 4150 00542
BARCODE|||||||||||| ETC
0580001-0700542G

With regards the resistor the last time I checked
first colour green=2
second colour red =5
third colour yellow multiplier=10000
fourth colour gold=5% tolerance

this gives 25x10000 + or - 5%

this =250000 ohms

250kohms + or - 5%

This resistor was checked using a fluke multimeter with an autoranging readout since the value of this resistor was 1 this shows that it was open circuited.

regards.

 

[Agile]

Er.. green is 5 and red is 2 ??? Yellow is 4 which in the third position means four zeros. That would be 520 k.

Have you measured a few resistors of know value, like 1 M to see how it reads them?

It seems that the resistor is not "blown" which usually is used to mean blown up and all charred! Instead you THINK that its open circuit.

I am not convinced by your testing though!

And how did you stumble on just this resistor?

Tony

 

[tiggerpussy]

Sorry agile you just rattled me last night (and i was on the phone whilst composing my post to you) you can see from my previous post its red green yellow gold and as regard testing i took the board off and went through all the resistors and diodes after following the power supply through the hw circuit then the ch circuit where there is power into the resistor in question and no power out.
I'm not really asking how to test just if anyone has any experience of a common fault I do believe in my own test results but normally when an purely solid state component fails there is normally a root cause but obviously since you don't know the resistor and you want to nit pick you are un aware of such a fault?
I'm not even sure if you know the board at all as I gave you all the data off the board and you still insist on nit picking.
I was under the impression these forums were meant to be helpful,
anyway its 10.21 and i'm off to the plumbers merchants so thanks anyway


regards