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 Post subject: Heathkit IT-28
PostPosted: May Wed 16, 2018 4:51 pm 
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Joined: Mar Sat 14, 2009 5:56 pm
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Location: RI, 02885
I acquired a Heathkit IT-28 this past weekend from a fellow ARFer. When I began checking it out I found high physical resistance in rotating the pots. One takes significant effort to turn and the other takes considerable effort to rotate. I have tried WD-40 but the improvement was slight. Does anyone know if the original assembler may have done something to the pots that is reversible? I tried dismounting the tightest one but it seemed to make no difference in its operation once off the panel. In the meantime I will be looking in my parts piles for a pair of 1K Wire-wound pots. From their size I am guessing 2 Watts should be adequate. Any helpful comments will be welcome regarding repair of the pots or Wattage rating for replacements. Thank you.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Wed 16, 2018 5:15 pm 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: The Old Dominion VA 23518
Modified somehow ?

The manual lists one 1K pot, the other a 100K. Be sure and check the values you have against the manual before replacing them.

A flush with Naptha usually frees up pots for me, followed by either some Caig D5 or WD40.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Wed 16, 2018 6:41 pm 
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Location: RI, 02885
Thank you for the input, Brian. The pots I am working on are the Balance Control and Power Factor. Both are P/N 11-101 (1K) and the schematic has both shown as 1K. I have a complete scan of the Assembly Manual (P/N 595-991-03 dated 1968) and the instructions cite the 11-101 being installed in those positions so I'm fairly certain they are correct. I will try some more intense cleaners since they are wire-wound and not as prone to damage from chemicals as a carbon pot will be. I'll just have to be careful not to hit other components with any harsh cleaners. They both did ease up a smidge with my application of WD-40 but I thought I would ask here if anyone had the same experience with the pots or if they may have been damaged through mishandling by the original assembler. For someone to have caused the same damage to two identical parts is pretty unlikely.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Wed 16, 2018 6:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Fernandina Beach, FL
Don't give up! Don't buy anything. Try WD-40 and a little heat. More than likely, the grease from the factory, what, 50-60 years ago? Has turned to glue. You should be able to free them up with lubricant and/or heat.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Wed 16, 2018 6:46 pm 
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Location: Mpls, Minnesota
Keep working the WD 40 in there , they will loosen up.

Dave


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 Post subject: Re: Heathkit IT-28
PostPosted: May Wed 16, 2018 7:56 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Albuquerque, NM 87123
Those controls had some red stuff that might have been insulation for the wire; when they are cleaned it sometimes gets on the shaft. I just use heat, acetone and then oil after it loosens up. Both those controls are 1k. BTW, I have seen some of those controls that needed the contact area of the wire to be cleaned thoroughly with alcohol and a swab.


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 Post subject: Re: Heathkit IT-28
PostPosted: May Wed 16, 2018 8:39 pm 
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Location: The Old Dominion VA 23518
Bugman wrote:
Thank you for the input, Brian. The pots I am working on are the Balance Control and Power Factor. Both are P/N 11-101 (1K) and the schematic has both shown as 1K. I have a complete scan of the Assembly Manual (P/N 595-991-03 dated 1968) and the instructions cite the 11-101 being installed in those positions so I'm fairly certain they are correct. I will try some more intense cleaners since they are wire-wound and not as prone to damage from chemicals as a carbon pot will be. I'll just have to be careful not to hit other components with any harsh cleaners. They both did ease up a smidge with my application of WD-40 but I thought I would ask here if anyone had the same experience with the pots or if they may have been damaged through mishandling by the original assembler. For someone to have caused the same damage to two identical parts is pretty unlikely.


Yeah, I see now - the manual doesn't show the units per assembly - (2) 11-101 1K pots and (3) 10-56 100K calibration pots.
For Naptha, I use lighter fluid - small container=all I'll need, and cheaper than the cans at HD and Lowes. It's pretty much a universal solvent, and evaporates nicely. Acetone has ruined too many things for me. I do make 95/5 Isopropyl/Acetone to make a defluxing agent.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Wed 16, 2018 9:11 pm 
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Joined: Mar Sat 14, 2009 5:56 pm
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Location: RI, 02885
Thank you all for the useful feedback. I'll work on it this evening. I figured someone would have found the same issue I encountered since so many Heathkits were out there.
My next decision will be choosing which capacitor tester will be my go-to tester.
I have a General Radio 740-B Capacitance Bridge, a Sprague TO-4 Tel-Ohmike and this Heathkit IT-28. My PACO C25 really doesn't count as a proper tester since it can't apply high voltage.
I just can't resist picking up any vintage test equipment that I run across an I'm running out of space to keep them.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Thu 17, 2018 1:44 am 
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Joined: Mar Sat 14, 2009 5:56 pm
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Location: RI, 02885
After following the above advice offered, the pots are turning smoothly. Now I can proceed with the restoration. I thank all that posted and appreciate your help.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Thu 17, 2018 11:43 am 
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Joined: Jun Fri 19, 2009 6:34 pm
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Location: Long Island
One word to the wise: don't spray DeOxIt into pots! It dissolves the carbon tracks on some of them.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Thu 17, 2018 11:50 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 17931
Location: Albuquerque, NM 87123
Chris108 wrote:
One word to the wise: don't spray DeOxIt into pots! It dissolves the carbon tracks on some of them.


Sure it does. That's why I've been using it for 30+ years.


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 Post subject: Re: Heathkit IT-28
PostPosted: May Thu 17, 2018 12:06 pm 
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Joined: Jun Fri 19, 2009 6:34 pm
Posts: 8066
Location: Long Island
DeOxIt did not exist 30 years ago. It was called Cramolin back then, and it was a different formula.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Thu 17, 2018 2:59 pm 
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Joined: Mar Sat 14, 2009 5:56 pm
Posts: 4262
Location: RI, 02885
I used Naptha and WD-40 to release the pots and the pots are wire-wound so DeOxit would have had no ill effect anyway. I had it as a back-up in the event the other methods didn't work.
I still appreciate the input from the responders and thank all. Now I will recap the unit and check the other components so I can return it to a serviceable state.

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 Post subject: Re: Heathkit IT-28
PostPosted: May Thu 17, 2018 3:03 pm 
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Joined: Jan Thu 24, 2013 11:50 pm
Posts: 2850
Location: Bristol, Rhode Island
Hi Pat,

Hope all's well! So you are back in Warren? :)
I don't know if this is the same issue, but on some old sets I've had to heat the pot shaft with a soldering iron to get it to loosen up the grease etc and get it to move; particularly with German pots.
Obviously when it cools off it becomes difficult to spin again, but then Ill just end up opening the pot and cleaning it if I determine that old congealed grease/lubricant is the culprit. Good luck!


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 Post subject: Re: Heathkit IT-28
PostPosted: May Thu 17, 2018 3:27 pm 
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Joined: Mar Sat 14, 2009 5:56 pm
Posts: 4262
Location: RI, 02885
I Ted,

Yes, I'm around doin' the same old stuff. Lots of new acquisitions making the piles deeper. The Heathkit issue is resolved due to the suggestions here. I hadn't thought about using Naptha but tried it and it did the job in conjunction with the WD-40. Drop by if you get bored.

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