Heathkit HO-10 how to use with transceiver

[N9AXl]

I got a working Heathkit HO-10. It appears that it's just connected in line between the rig and the tuner.

On page 44 of the manual it talks about running a cable into the microphone input.  This seems confusing.

Right now I'm planning to use it with my Icom 751. I have an HT37 so this will be more useful with that

[Pete, WA2CWA]

I got a working Heathkit HO-10. It appears that it's just connected in line between the rig and the tuner.

On page 44 of the manual it talks about running a cable into the microphone input.  This seems confusing.

Right now I'm planning to use it with my Icom 751. I have an HT37 so this will be more useful with that

The Figures 2, 3, and 4 shows it quite clearly if you want to view the transmit envelope or AF/RF trapezoid patterns. The setup can be used for checking linearity using an exciter and linear amplifier. The TONE output of the HO-10 provides either a single tone or two-tone signal that goes into the microphone input of the exciter/transmitter.

[N3GTE]

Just as an side if the HV filter for the crt haven't been replaced they can take out the power transformer render it worthless. It's a common problem w/these sets.

Terry N3GTE

[N9AXl]

This one has had everything replaced except that. It's a four unit electrolytic c23 c24 c28 c29judging from the manual and schematic,I plan to replace it before I power it up.
Is this the one you meant?

[N3GTE]

No, It would be C-30 and 31. They may a little difficult to source as they are .15mfd @ 2KV.

Terry N3GTE

[N9AXl]

They are $3 each at hvstuff.com. They sell them for people making Tesla coils.
 I've ordered the assembly manual for this.Given the high voltages involved that and a pair of Bellsouth NOS electrical gloves rated to 7kv seems in order. I want to make darn sure those caps are discharged.

Most of the other caps have been replaced so I think I can bring it up on a Variac safely. If it seems to work I will defer the replacement of parts until later. As you can see from the photo someone has done a nice job of putting some caps in series to replace the HV caps. I see that what appears to be the 1000 ohm 1 watt resistor is broken -- center of photo.

Any thoughts on how long to reform the caps and at what voltage steps? I know that's no substitute for replacement but since I have a Variac....

[N3GTE]

Looks like your 2 HV caps that are series are .15mfd. This equals .075mfd not .15mfd as per the schematic. Tnx for the link I'll have to pickup a pair for my old ho10.
All of the caps look pretty new so I don't know that there is any reforming to be done (if you believe in that process). If anything I would use the variac to soft start it over 20 or 30 sec.
Don't if you've seen this:   http://amfone.net/Amforum/index.php?topic=10496.0

GL
Terry N3GTE

[N9AXl]

Thanks. I will have to think about why someone would do this and want 50% of the capacitance.

[KA2DZT]

Thanks. I will have to think about why someone would do this and want 50% of the capacitance.

To get a higher voltage rating, commonly done.  Those caps should be checked for leakage.  Put a high voltage on one lead and measure for any DC voltage on the other end.  If there is any leakage, replace them.  A microwave oven cap would work but probably not enough room for one.

[N9AXl]

But what's the operational benefit?  I can see someone not having a single unit with the right voltage rating so they put two in series to make the higher value, but wouldn't cutting the capacitance in half negatively impact the unit's performance?   (I know I'm over analyzing a 50 year old piece of equipment but anyway...)

[KA2DZT]

Generally the filtering for a high voltage CRT supply uses very little capacitance for filtering.  Most all old TVs used only 500pfd for filtering.  Why only 500pfd??  The high voltage supply voltage was supply by the flyback xfmr which was running at 15kHrz.  At 15kHrz you didn't need much capacitance.  In your scope I think the high voltage runs at 60 cycles so you need more capacitance.  Since the load is probably less than 1 ma you don't need much capacitance.  Something around .2mfd or less should be more than enough.

Fred

[WBear2GCR]

Guessing. It was done because A) it was good enough, b) it was a mistake and they thought that series caps
added in capacitance, not halved, or c) none of the above. 

I'd probably look for some HV ceramic caps... pretty easy to find 7 - 10kv.

[N9AXl]

Thanks. I have the assembly manual coming so I will give this a good going over and replace everything to spec. It looks like some replacements have already been done, but the HV caps and resistors obviously need to be looked at.

[Pete, WA2CWA]

Thanks. I have the assembly manual coming so I will give this a good going over and replace everything to spec. It looks like some replacements have already been done, but the HV caps and resistors obviously need to be looked at.

You can buy the re-cap and/or resistor replacement kit from Hayseed Hamfest:
https://hayseedhamfest.com/collections/heathkit/products/ho-10-re-cap-kit
Saves a lot of time and maybe even $$ searching around for all the correct stuff from various vendors yourself.

[N9AXl]

Yep. That's who I deal with. Great people, good prices, very easy to work with. Highly recommended.  A custom cap for my Johnson T/R switch I'm restoring was $31.95 and shipping. They will do an entire kit for a Heathkit DX-100 for $100.

I have installed the kit and the HO-10 fired right up. It works fine once I got the proper adjustments from the manual. Have it hooked up to the rig and it displays perfectly. Nice bright trace. No issues.  Not a great instrument but for basic info about my signal it seems to do just fine.