Author Topic: heathkit sb 614  (Read 999 times)

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Offline kinkydoints

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heathkit sb 614
« on: January 12, 2017, 05:53:39 PM »
I have gotten my HV circuit kit to replace caps and resistors on the high voltage circuit , on examination looks like these parts may have been changed at some point. There are two 70 mf caps next to the 3   0.1mfd +-10% 1600vdc cdent caps...these two aluminum caps do look original see pic for the location . The parts book call for these to be 70 mfd  electrolytic... but no idea of the voltage of these two big caps. Id like to change them also.  they are at c128 c124 on the board. on page 25

Offline kinkydoints

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Re: heathkit sb 614
« Reply #1 on: January 13, 2017, 06:49:18 PM »
Im not a electronic wiz but if I can read the schematic the voltage is 290 vdc indicated by a oval with the 290 in it going to c128 70 mfd cap , c128 is grounded to circuit board ground, 209 vdc continues to r156 and r155 by zd 101 zd 102 to the c124 cap 70 mfd  to +180v "source" looking at the fold out schematic on page 103. I will need a 290 v or better cap in these two spots?  Im trying here guys.  but are caps listed a ac volts?

Offline k7rmj

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Re: heathkit sb 614
« Reply #2 on: January 13, 2017, 10:35:49 PM »
I took a peek at your schematic in the manual. They both C124 and C128 are on the line that provides 190 VDC. The voltage coming off the bridge rectifier appears to be 290 VAC. I would suggest 350 to 450 VDC for those two caps just to be on the safe side. It may be easier to find 450 V caps but anything from 350 V to 450 V should be safe, IMHO. Anything over 450 V would be okay too.
Good luck with it and let us know how you make out.
73  DE K7RMJ  Frank

Offline kinkydoints

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Re: heathkit sb 614
« Reply #3 on: January 14, 2017, 07:34:32 AM »
Thanks for the feedback k7rmj Im getting all my parts together and will getthis nice old monitor back to work again.

Offline k7rmj

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Re: heathkit sb 614
« Reply #4 on: January 14, 2017, 06:39:36 PM »
Glad I could help a little. Good luck with it and keep us posted on progress.
73 DE K7RMJ  Frank

Offline kinkydoints

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Re: heathkit sb 614
« Reply #5 on: January 17, 2017, 08:22:48 PM »
Ok Got my replacement caps in... these are not the HV kit these are to replace the ones that looked original and were not in the HV kit.. Now for the caps that came with the HV circuit kit . there are three 1600 v .1mfd caps in the kit and look similar to the ones that are in the unit now, as im looking at this unit these have been replaced before...but look at the three cap set, the center is in opposite of the two that are on each side. OK question are these caps polarized ? there are no markings to pos or neg , both leads are the same length . as I look at the new ones there is a folded over lead ,all of these caps are printed on and are in the same orientation ,as far as the print on the cap and the folded end. pos or neg that is the question?
would a reversed cap cause issues down the line on other components?  thanks 

Offline kinkydoints

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Re: heathkit sb 614
« Reply #6 on: January 17, 2017, 08:28:09 PM »
sorry about the GIANT pics ...

Offline kinkydoints

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Re: heathkit sb 614
« Reply #7 on: January 22, 2017, 03:31:16 PM »
update on this sb614 have replaced caps in the hv circuit and tested on the bench , I have a link to a vid here.
https://vid.me/3EUg    seems to be fine ! thanks guys

Offline k7rmj

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Re: heathkit sb 614
« Reply #8 on: January 26, 2017, 03:44:11 PM »
Congarats Kinky. Glad to hear you got it sorted out.

Online Radio Tech

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Re: heathkit sb 614
« Reply #9 on: January 26, 2017, 08:45:25 PM »
Good job on getting her up and running again!
Buddy kc4umo

Offline kinkydoints

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Re: heathkit sb 614
« Reply #10 on: January 27, 2017, 10:29:04 AM »
Im learning everyday , helps as far as some of the categories that are covered in the test for my ham ticket. I am also replacing all electrolytic caps to new ones , some of the original ones I can not match up exactly , I have read that if the mf rating is not exact than the next closer higher is the rule of thumb. most of the voltages are also close , like 10 mf at 9v turned into new 30 mf at 15 volts.   50mf is a 100mf and the  250mf went to 300mf. how about those (4 )green 10K ohm 7watt round resistors can I upgrade those with new? what would you recommend for replacements ?    (1) 2K ohm 10 watt square wire wound? t I think they are in the pic on this post. I like working on my stuff  " indoors" not like my full time job...

Offline k7rmj

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Re: heathkit sb 614
« Reply #11 on: January 31, 2017, 04:01:54 PM »
For the resistors you should keep the resistance value the same. Keep the same number of ohms. It actually depends on which part of the circuit the resistor is in. But, if it functions as a dropping resistor and you change the value of it the voltage drop will also change and could throw the required voltage or the current way off. That could be a disaster in some circuits. The power rating of the resistor is not as critical as long as your replacement is rated for MORE power than the original.

I'm not real sure on the value of the caps. But, I would thing that you want to keep their values close to the original values. Again, it depends on the circuit the cap is used in. If you had to replace a 10 uF cap I would not go over 20 uF and I would feel real uneasy about that too. a 12 uF would be a better choice. But, again, that is just my opinion and I might be full or old wives tales LOL. It wouldn't be the first time either.

Just my 2 cents. Good luck with it.

73 DE K7RMJ  Frank

Offline kinkydoints

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Re: heathkit sb 614
« Reply #12 on: February 05, 2017, 07:26:02 PM »
K7rmj thanks for the advise , I did replace the two high 50mf caps with the 10mf . they were both 16 volt , so no changes to the circuit they where in.. I still would like to get those old green resistors ( 4 ) as well as that square wire wound changed, maybe with a newer type? they seem really long, as far as resistors go, new ones might not be that long even with the leads extended to the though holes? no worries I like working on this unit. I wonder if the work I have done can be tested in a shop that knows the in's and out's of these Heathkit  monitors.

Offline kinkydoints

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my heathkit sb 614 and new equipment...
« Reply #13 on: November 16, 2017, 07:56:29 PM »
well Im hooked...after the sb614 station monitor I purchased and recapped I am looking to get some equipment to check and learn how to do a basic Alignment   ...the next addition is a PC USB 2CH 60M 200MS/s Digital Oscilloscope 60M Spectrum analyzer Data Recorder , as well as a DANIU FY3224S (FY3200S-24M) 24MHz Dual-channel Arbitrary Waveform DDS Function Signal Generator Sine Square Wave Sweep Counter, VICTOR VC3165 110V-220V Professional Precision Frequency Counter Meter. also got a cheap cobra 19 plus . to do these tests on. I need to get some kind of an attenuator ? are these a good start? cheap ya...
point me toward some reading material that covers old school  Alignments and tools? Did I go too fast here in my equipment? as far as the 11 meter band will that FY3224S work in this application.  thanks