HO-10 question

[Tom NØJMY]

I don't want to give any impression that I think I'm an expert, Sandy, 
because I'm not, but I've always heard that the fixed resistors in that 
neck of the woods are highly suspect.  I'm thinking back to the research 
we did when we developed the HO-10, HO-13, et al re-cap kits.

Unlike the other Hayseed Hamfest re-cap kits, we decided to offer an 
optional replacement resistor kit for the resistors that were voted 
"most likely to fail" (we came up with 13 in the '13).  In the not 
inconsiderable amount of research we did, it became clear that by far 
and away, the resistors associated with the focus and intensity (i.e. 
the HV bias) were the ones that failed most frequently.  By "fail" I'm 
including going way high in "R".

These would be R70, R72, R74, R75, and possibly R80.  They are 3.3M, 
330K, 330K, 100K, and 220K (1 watt), respectively.  If you replace one 
or more, I would suggest doing what we do with our kits, which is use 
film caps, bump the voltage rating up to 500V and replace the 1/2 watt 
units with 1 watt, the 1 watt with 2 watts.

Of course there's 4 or 5 caps in that bias circuit worth looking at, 
too.  We felt it advisable to put the 2 - .15 uF @ 1.6kV caps in our 
kit, as a matter of fact.

I hope this at least gets you a place to start.  Be careful around that 
-1400 VDC.  I still have a 30-year-old tatoo on my left forearm, 
courtesy of an HO-13.

73,
Tom NØJMY .   .

Hayseed Hamfest Co. - Multi-section Can Capacitors
for vintage Heathkit, Drake, Halli, Hammy, more...
www.hayseedhamfest.com



Alexander N. Gerli, Sr. wrote:
> Hi, gang!
> 
> My HO-10 is behaving oddly.comes up fine from cold. Only problem appears to
> be a wavy horizontal trace. I would imagine that's due to some ac getting by
> the hv rectifier chain.
> 
> However, after about a half hour, the trace dot goes WAY out of focus, into
> a fuzzy, square block, with the focus and intensity controls not working.
> The vert and horiz position controls still work just fine.
> 
> Suggestions, please??
> 
> 73,
> 
> Sandy AC1Y
>  
> Alexander N. (Sandy) Gerli, Sr.
> 4012 Bristol Road
> Durham, NC  27707-5403
> (919) 489-9638
> CCA #AC96-00001
>  
> REAL radios glow in the dark!!!!

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