[AMRadio] Heath HO 10 Monitor Scope


Larry Knapp kc8jx at yahoo.com
Sun Feb 24 14:27:57 EST 2008


John, perhaps this copied email I saved will help you and others repairing the Heathkit scopes. 
Perhaps some of this can help....Applies to SB-6510 and HO-10

73, Larry KC8JX
Owner of a SB-610 and two HO-10's
***********************************************************************
March 14, 2007:  By "carl lowry" <l_carlj at bellsouth.net>

I redo the SB-610s everyday.  Infact there are 8 of them in my workshop right now to be restored. 
The 610s were manufactured by Heathkit between 1968 and 1972. They are older than some of our
recent Hams.. but many of us broke our teeth on Heathkit.   Every 610 I get in here I replace
"all" the resistors and "all" the caps. It takes me about 15 hours to undo & replace all the
components. When the Control Pots are stiff or frozen you've got to disassemble them & clean them
up & relub. The Selenium Rectifiers I replace with 1N4007 Diodes.  I have really not found any
resistors or caps in the units to spec at what they originally were when first manufactured. 
After all they are 35 years vintage. We all change after those many years.  The "lack" of trace
wave width (TWW) can be contributed to the .05mfd cap going to pin 3 on Horizonal Gain Pot which
is a 1 megohm.  Also look at the Horizonal Position Pot circuit which has a .1mfd cap on pin 3. 
Like one of the other guys mentioned "Look at the Intensity" circuit.  Also look at the Focus Pot
next to it.  I would replace the 2 Caps and the 3 resistors ( 330k & 3.3m ).  If you need the
Mouser Part Numbers please e-mail me & I will be glad to Fax you all the Mouser part numbers. Good
luck. Carl. 
******************************
--- John King <k5pgw at yahoo.com> wrote:
> Have replaced bad 3RP1 cathode tube in my HO 10 and
> tested all other tubes. Have changed the two
> .15 at 1600VDC capacitors.
> 
> It is working however not up to PAR. All controls
> work. The current problem is that when in the
> trapezoid pattern monitoring AM transmitted signal,
> the horizontal width of the trapezoid doesn't
> completely fill out to a symetrical point. The
> horizontal position and horizontal gain pots work
> except that there doesn't seem to be enough horizontal
> gain to cause the trapezoid to fully display the full
> signal.
> 
> I have a properly working SB 610 that shows clearly my
> transmitted AM signal. The HO 10 doesn't fill out the
> trapezoid symetrically to a point.
> 
> I suspect a resistor in the horizontal gain circuit
> having changed value or maybe a suspect capacitor. Are
> there any commonly known culprits that cause this loss
> of horizontal gain? Naturally, I am lazy by nature,
> and would rather "pick your brains" than use my feeble
> brain. What are your thoughts based on your vast
> knowledge and EXPERIENCE??? Thanks and 73, John, K5PGW



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