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Author Topic: BC-614 Mods  (Read 17813 times)
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n9ami
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« Reply #25 on: December 20, 2020, 09:50:52 PM »

Not sure what I am doing yet. However I need to sort out how to properly key the thing using the 614.
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W2PFY
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« Reply #26 on: May 01, 2021, 11:29:28 AM »

Hello John, did you get this 610 on the air yet? I'll be back up and running this month at my amp. I forget where you are but perhaps we can meet up on 40 meters?

Regards,

Terry
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n9ami
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« Reply #27 on: May 01, 2021, 12:01:20 PM »

Oh 610 has been up and running nice.  Had to replace a 807 that went south so did both and discovered both parasitic resistors on those sockets were poof so repaired those. Who knows how long that's been like that or when the one 807 went did it take them out? Who knows.. but repaired and running nice.  The 614 is another story. I am back using my ranger for the speech amp for now.
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W2PFY
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« Reply #28 on: May 04, 2021, 03:27:38 PM »

Yes I too had an 807 problem. The glass on one 807 cracked and obviously air got in and that caused the circuit to draw too much screen current and took out the 22Kohm screen resistors. I replaced them with 1/2 watt resistors like was called for only to have them go south shortly thereafter. I then replaced them with (2) -1 watt resistors in parallel to get me close to the 22K I needed.

I often threatened that if resistors went bad again that I would install a rheostat in the screen circuit to vary the 807's output to the 250TH final tube. As it stands, if you have too much final grid drive, the only way to reduce that drive is to de-tune the exciter? I never tested the output for harmonics but they must be more prevalent when the only way to vary the drive is to de-tune it?

Anyhow, it's been about ten years and the screen circuit is still running strong?

Something to think about  Grin Grin 
 
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n5ama
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« Reply #29 on: October 18, 2023, 09:34:11 AM »

This info is a bit dated but is exactly what I was looking for.
Thanks a bunch for providing me a starting point for my BC-610-E/BC-614-I project!!

My BC-610-E works very well so my restoration/modifications will target the 614 unit.
I planned to recap the 614 but keep things as original as possible. Both units were original
Army MARS units and are beautiful cosmetically. The only issue with then 610-E is the
bakelite front of the filament switch broke off, so the metal piece inside of the switch is a
little hard to reach but it works. I do have a replacement for it but the multipole switch on the
other side of the switch assembly is shot. Iím guessing that switch assembly is unobtainum
and would be next to impossible to find since it was probably made specifically for this rig.

I have a 614-E but it was pulled out of itís original cabinet and has some undocumented mods
and has two non-standard meters. I would love to find another 614-E in original condition (or
at least with a original front panel and case) but I know the chances are about as good as
finding that 610-E switch assembly.

Anyway, thanks for the head start on my project!!!

Tom N5AMA

 
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n9ami
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« Reply #30 on: October 18, 2023, 10:53:51 AM »

I have my 614 sitting under the desk and don't use it. I use a ranger speach amp and the vfo for the 610 better audio and better stable vfo in my view. 614s are around keep a saved search on flea bay. I will keep this one in case I ever sell my 610H.
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n5ama
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« Reply #31 on: October 18, 2023, 11:37:28 AM »

Thanks for the reply!

I don't have a Ranger but even if I did I would prefer using the 614 to drive my 610-E. Quite awhile back I built a VFO to use with a 610-I (sold it years ago but kept the VFO) using a homebrew regulated supply with a Collins PTO which I use through a crystal I've modified to plug into the TU of the band I want to operate. The PTO is very stable and included a test button to check frequency since the National dial I'm using doesn't indicate actual frequency. I don't operate many frequencies and marking the indicated dial position gets me back real close to the group frequency and the spot button allows me to zero beat.

I appreciate your and W2PFY's work and comments to get me started.
Have a great week,
Tom N5AMA
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n5ama
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« Reply #32 on: October 30, 2023, 10:01:14 AM »

I have reversed the mods on a 614-I to use with my 610-E transmitter. It had a non-standard mic socket which I swapped for a 3/16Ē mic jack and had a relay hooked up for keying (??) which I pulled off the chassis and filled in the hole. The cosmetics is real nice on this unit except for the front panel mic jack (I shot some black crinkle to help that issue). 

Iíve recapped with .15/400 orange drops and the electrolytics as per the suggestions in the earlier comments. The unit seems to work well and Iíll try it on the local 80m rag chew later this week.

Thanks and have a great week,
Tom N5AMA
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n5ama
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« Reply #33 on: October 30, 2023, 08:10:10 PM »

A pic of the setup. The two pieces of gear on the BC-614-I is the Collins PTO I use for a supply and the box that takes the place of the JB-70. I would like to find a real JB-70 to go with the rig. I'm also trying to find a nice SX-28 to go with the setup. I've got one targeted but it's way out of state and I'm afraid shipping is going to be prohibitive.

It's funny that I also happen to have a PE-95 genset that was mentioned in the manual (I'm not moving it into the shack to power the BC-610-E and gear). 

Tom N5AMA


* BC-610-E_1.jpg (880.73 KB, 1512x2016 - viewed 86 times.)
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Tom W2ILA
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« Reply #34 on: October 31, 2023, 09:17:48 AM »

Looking forward to hearing that setup during this winter. 
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n5ama
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« Reply #35 on: October 31, 2023, 09:35:58 AM »

Thanks for the reply!! I've yet to put it on the air. I'll do that with the morning rag chew gang to get feedback on audio quality and any other issues.

Have a great week,
Tom
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n5ama
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« Reply #36 on: November 02, 2023, 09:54:29 PM »

Well, minor setback occurred this morning. No drive so no output. Found a blown 5A fuse, replaced it and still no joy. Saw the regulators unlit so checked the 5Z3 rectifier and even though the glass envelope was unbroken, it appears that the smoke got out.

I had no spares for some reason so I may wire a 5U4 into a 4 pin socket just to try it out until I get a 5Z3 replacement. I'm guessing the 5Z3 just decided to give it up but not sure why the fuse blew.

Tom N5AMA
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n5ama
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« Reply #37 on: November 03, 2023, 08:47:05 PM »

I made an adapter to replace the 5Z3 with a 5U4G until the replacement arrives. The 5U4G appears to work good and the fuse doesn't blow now but there are issues that remain.

When I attempt to tune it up either with a crystal, the M.O. or the VFO, the first operation after letting it warm up and turning the exciter plate power on, is to set the excitation meter switch to int. amp grid and adjust the doubler knob on the tuning unit to maximum meter reading. As soon as I switch the exciter plate on, the meter goes to half scale (about 8ma). Within a few seconds the meter climbs to full scale (15ma). The doubler knob will reduce the meter a small amount but not much. The int. amp. grid current is way higher than normal.

I checked the voltages on the two terminal strips under the exciter chassis and all seems normal except Terminal Strip #1 position 7 is supposed to have 100vac and it has 9vac. Position 9 is suppose to have -180vdc  and it has no voltage present.

Terminal Strip #2 positions 5,6&7 are suppose to have -180vdc and it has -9vdc.

I haven't traced these test points on the schematic yet but hope to have a chance to do that tonight.

Either the 5Z3 failed and caused some collateral damage or something in the exciter failed and took out the 5Z3 and the fuse.

Does this sound familiar to anyone familiar with the BC-610?

Any suggestions greatly appreciated!

Tom N5AMA 
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W2PFY
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« Reply #38 on: November 03, 2023, 10:49:32 PM »

Hi Tom, I just put diodes in the tube socket. That takes care of short life tubes and it provides more plate voltage to the exciter giving your more drive power to the 250TH. I just keep the meter set to read the 250TH grid current and twirl the knobs for max final grid drive. On 160 and 75 meters you should be able to get at least 100 mills of drive with a good 250TH. People on eBay sell solid state replacement rectifier tubes if you don't want to build your own. For whatever reason, my 610 burns through 6V6 tubes but I have many spares. Old rusty metal tubes work well if you have any in your junk box. Not all 807's are born equal, a given pair will sometime produce more drive than another pair despite being NOS. Good luck finding that low voltage problem. I'm 82 now so I am slowing down and can't be of much help. If I can find my 610 manual, I'll follow along as best I can.

Have fun, de Terry W2PFY
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n5ama
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« Reply #39 on: November 04, 2023, 07:28:38 AM »

Good morning Terry! Thanks for the info. The diode installation in the 4 pin socket would have probably been the quickest solution for the dead 5Z3 but I looked at the specs and found the 5U4G to be a good match and had a few around so used that for the fix. I also didnít want to incorporate any non-standard such as higher voltage to confuse trouble shooting the other voltage issues. I also agree that using the diodes will be a bit less load on the filament transformer so Iíll probably do the SS diode thing after I sort out my other issue.

Working under the exciter chassis and checking voltages is not the easiest thing my old 76 year old back has done recently but itís sort of necessary. I do have an original manual for this rig and some of the illustrations are funny. Iím not sure if they are a result of our military or of the Hallicrafters group doing their thing but they are entertaining.

Iíll just have to get in the rig and paw around for awhile to see if I can locate the problem (s). I was just hoping someone with more experience on the 610 would recognize the problem and offer a suggestion.

Thanks and have a great weekend,
Tom N5AMA
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