Heathkit HO-10 Monitor Scope for HF

[Naysayer]

Got this from eBay a weeks or 2 ago. Ordered new caps and some select resistors. Input adjustable rear panel from 1/2w to 1kw (SSB I presume) just a jumper with a signal tap to scope inputs.
It's old but limited features so it's not so complicated I'd avoid using it. Will it have "use value" or just a pretty green light? IDK but I'll get it set per the manual and see.

Inside was in good shape all stock w/ some evidence of smoking environment. Orig Builder did a fine job with the solid PTP wiring, purposefully bent leads. Reluctant about replacing everything. Vertical gain pot (1MO) somehow destroyed, shaft would not turn, inside wiper broken/bent somehow. My 1st project since getting new LCR meter so it’s an opportunity learn using it.
All tubes tested good.

 

[nomadradio]

All tubes tested good.

That sure works in your favor. Seems to me there's a 12-pin "compactron" tube in there, maybe a 6C10 that has three triodes in it. Saves space, but that one has gotten expensive. Turns out to have been used in some high-end guitar amp of the 60s.

I used one of these decades ago. Decided to set up a FT-101 (no suffix letter) at home when the kids were young. None of them got really interested, but found I couldn't tune up a radio without a 'scope. Always had one on hand at work for decades. Took one of these home after a re-cap and it fixed my problem, especially for RTTY. Made tuning the receiver a lot better. It went onto the shelf a while later when the FT went back to work as a bench radio. A later-version SB610 came in for service and needed a CRT. Tried to unplug mine and the lead wires came out of the hollow pins at the base of the CRT. They had rusted/rotted out over the years.

Oops. But I located a new CRT for the customer so he went home happy. Pretty sure the sad HO-10 with the ruined CRT base is still hiding in a corner waiting for doomsday. Anybody want one, cheap?

73

 

[Naysayer]

Nearly a Month later, got the new parts installed into scope but have not yet applied power. I planned on replacing every resistor pair (same value) only. After I measured a few, it was obvious they all need replacing. They all show far higher resistance than their color band values (like: 330k being over 400k), So I am using lots of braid. Replaced another Pot that was jumpy and rebuilt another to restore smooth operation. Not much space inside.

Oh right, got my General CSCE last night. Tested in-person at a GLAARG site in Brooklyn sponsored by the NYC Resistor collective. Never went there before but they have a nice space/workshop area. I am eager to use new privileges but need to wrap up the scope before I start something else or I'll forget what goes where.

I downloaded the condensed manual (HO-10 Monitor Scope) but there are no wiring instructions. Was there a separate Assembly Manual? I recall such instructions in older kits I had in the early 70's. Original Builder made frequent use of unused tube-socket pins as connecting posts for unrelated wires/components. Efficient yes but 5 decades later, confusing AAF. The manual available online lists the parts, operation of scope, diagrams and trouble-shooting but nothing about assembly.

Diagram Convention Question
Where the diagram shows connections and/or wires heading off-page with a note (like: "B+ Hi 380v") that means it connects to any other place on the diagram where the same note appears, right?? If it was a Test Point, it would say so. This design is likely older than I am.

Just want to work 40M as soon as I can move scope off work table.

later, neil