🚀 go-pugleaf

Arfa Daily wrote:
> "Sylvia Else" <sylvia@not.at.this.address> wrote in message 
> news:4961f0fa$0$25649$afc38c87@news.optusnet.com.au...
>> Ok, as I mentioned elsewhere in this thread, I managed to get the A/C 
>> working again by replacing Q1 and the 8.2 ohm resistor.
>>
>> Actually, I'd misread it, and when I looked more carefully, it realised it 
>> was 6.2 ohm, as is the other one on the board with the same markings 
>> (i.e., a not blown one). Nice standard value that.
>>
>> So now I have to replace the resistor with a fusible, but sourcing a 6.2 
>> ohm fusible is problematic.
>>
>> The situation is not made any easier because if the switching transistor 
>> fails by shorting out, then after it blows the fusible will have 340V 
>> across it.
>>
>> From the suppliers I now know about (thanks, Trevor), I can get a 0.5 watt 
>> 340V 4.7 ohm fusible. I propose to put it in series with a 1.5 ohm 1 watt 
>> non-fusible. My reasoning is that the 1.5 ohm resistor will have only 1/3 
>> the power dissipation, and will handle twice as much. Therefore the 4.7 
>> ohm will go open circuit before the 1.5 ohm could get hot enough to be a 
>> problem.
>>
>> Does this stand up?
>>
>> Sylvia.
>>
>>
> Are you absolutely sure that it is definitely 6.2 ohms ? That is a *very* 
> odd value, particularly for a fusible type ... FWIW, I really don't think 
> that the circuit would give a damn if you replaced it with a 6.8 ohm, which 
> is a standard value. Did you actually measure the one that's ok with an 
> accurate low ohms meter, and get a reading of 6.2 ? Seems to me that a grey 
> band and a blue band might easily be misread one for the other, with some of 
> the banding paints I've seen used over the years. I find that it is often 
> very easy to misread red for orange or brown, especially if the resistor 
> runs warm in normal use.

Blue Red Gold Gold = 6.2 ohms, 5%. It is in the E24 series, but I've 
certainly never seen one before.

When I made up an equivalent, my meter gave the same reading (allowing 
for tolerance) for the equivalent as it does for the identical resistor 
on the board.

So, yes, I'm pretty sure.

As for whether I could substitute a 6.8, maybe I could, though I'd have 
trouble getting one that has a 350 volt rating. The only supplier I know 
of that purports to have them doesn't give the rating. The suppliers 
that give ratings don't carry that value.

If I understood the circuit better, I'd be more comfortable about 
changing the value. The mere fact that an unusual value has been used 
gives me pause - maybe it's the value that's required there. Even if 
another value worked, I'd not know the ramifications.

Sylvia.