The AM Forum

I acquired an BC614 I and looking for a good listing of mods to throw at it. Someone was in it and replaced with orange drops which of course is good. But I want to dump the old microphone connectors because I have no carbon mic and want to put in a standard 1/4 and a XLR. I did do a internet search but came up with nada. Possibly Electric Radio of the past?

I can offer a little help but before that, what model 614 is it? C D E F G H or I model? They are mostly the same but some have a few extra features that may be or not be useful?

Terry

Thanks Terry,
  It is the I model.

John

with this mods work the bc614 better

I will print them out and take a look see thank you.

Ok John, I see you got some help already. For now I would strongly suggest that on the power transformer in the BC-614 that you remove the two caps going to the primary of T-103. They are C-103 & C-121. They will at some point explode and it may be quite a loud report when it happens. It happen to me on two different 614's. They were for keeping RF out on the primary and perhaps spikes on the line in a military setting where you could have had many BC-610 or other powerful transmitters in a close settings. You may choose to replace them as well but I would up the voltage rating on any caps you may choose to use as replacements.

I looked at those schematics that were provided PA3HCO and they are fine. I would like to know what you plan on doing before I might offer some further suggestions but you may have them in mind,so I'll wait ;D ;D. Some people just gut them out and use a straight forward audio circuit but I like to use as much as makes sense in these old radios. I operate a BC-610D and before that a C model.At this time I am not using the 614. I am looking for the D model 614 that has some additional features that I would like to try to use such as a remote telephone that is directly hooked to the transmitter via that D model 614. It won't work via the Bell system.lol  

You can download the manual here. Too large for this site.

https://bama.edebris.com/manuals/military/bc614/ (https://bama.edebris.com/manuals/military/bc614/)

Firstly thanks for your input. I opened up my 614 and see someone installed a bunch of orange drops in similar fashion to what I see in the schematics the other om sent on here.   

I have my 610 setup running nice with a Ranger for audio and vfo. It seems to work great. However I had a bug up my butt and thought running with a 614 would be better. Why I thought this I have no idea. Well for one I could watch the mod plate. Free up the ranger and use it for a lower power setup or amp. Now I am wondering if I can just put a meter in the circuit to watch the mod plate and call it good lol.

Anyhow back to the 614. I thought I could work with it and make the rig sound better with some mods like adding the TRS and XLR to run a nice audio rack. I am not a military radio guy so I know jack about most of the stuff military.

A couple things I found to question on mine. There are 2 wires (yellow tape circled in white) coming from the transformer that looking at the schematics would be used for some sort of outboard 120 volts? Possibly to run the 614 on separate power? A nice hole is in the back that looks like it might of had plug or sorts. Also there is a 2 pin microphone plug on the rear.    And a phantom wire (circled in red) that I have not traced as of yet.

Figure I better start with this stuff and post a few pics.

Modified photo with circles as described in my last post.

It looks like those two caps you have circled are the caps that I said could explode? So someone had figured that out or just did it because they are old?

Ahhh.. Okay well maybe someone knew what was going on with the 614s. I got this off of ebay.  Its not very pretty on the faceplate but that is no consequence at the moment.  I am waiting for a couple octal plugs and 8 conductor cable to get it wired up. 

Does that white wire that goes up by the two orange drops hook up to anything at the other end on the tube socket or are they just taped off? I have to run out soon to get some BO NAN NAWS. I can't spell it correctly anymore ;D and some other stuff so that when I wake up early in the morning, I'll have something to snack on and I'll not go into a panic fit ...

Therefor, I'll get back to you later or tomorrow..Have fun with it. I'll have a couple suggestions on the next flock of posts...

Terry

Its burred in big time and I spent about an hour poking around to find the other attachment point and nada so far. I will have at it again tomorrow.

What's this about? I must have missed something?

Terry

I was tracing the single white wire you asked about.

Okay the scoop on the white wire is its other end terminates at R114

Well I am sorry about that. I was talking about the two white wires that are hooked to the primary of the power transformer on that chassis and have the yellow tape on the other end. They must have been used to power it up at one point, but when property hooked up, it will receive power from the BC-610. You should just clip them out and discard as they might introduce hum just laying around in there.

I must have home built at least four cables to go between the bc-614 and the 610 over the years. Inside the 614 there is a cap that may short at some point and when it happens, whenever you turn the BC-610 on, the HV is keyed while the tubes are still cold and comes up to full power all by itself. It didn't hurt anything but it took me quite awhile to find it. I thought it was a short in the cable that I spoke about above and built another one but the problem was still there. I'll go thought the schematic and point out which cap it is. All you need to is clip it out of the circuit,as it serves no purpose as a civilian radio and the problem is fixed.

I have just two ideas about the audio circuit and I'll cover them later. Am I getting too overbearing at this point? Should I shut up for awhile ;D ;D

No your good. I was thinking of cutting those 2 wires out for sure like you mentioned. As far as the 614 to 610 I have a couple octal plugs coming and some 8 conductor cable ordered. Looks like its straight through 1 to 1 2 to 2 etc.

FYI appreciate your help

john

Yes it that simple John but I grew to hate building cables. If your very lucky, you can sometimes find the original cable on eBay or by putting and ad on here or QRZ. I have one and I am saving it for use with the D model 614 if I ever find one?

I have one more cable assy to build for my Chippewa amplifier and after that, there better be gold involved or I'm not building another :D :D

The cap that can short and key your transmitter is C-126. Attached is a copy with the cap circled in yellow. I hope! 

Alright good deal. I will snip that out.

So delving into the 614 I have here more I think I figured out what someone was doing. With the direct power fed out board IE the removed 2 wire to the power transformer and the 2 pin plug in the back going to the T102. I surmise someone was power the 614 separately and running the 100th girds direct with it.

So it's possible that they didn't want to build a cable and just used the output from T-102 to drive the next transformer in line on the 610?

Well they could of been using it for a bc transmitter or homebrew tx also.

Yes, I agree that anything is possible. If it was not an estate sale, perhaps you could ask the seller how it was used? I have had good luck with getting details. Sometimes there are eBay sellers visit ham fests and buy thing but probably not recently? Others  buy stuff from eBay at a low ball price and then flip it? Maybe your seller has some history?

Well anyhow, I'll get back to you in a couple days about ways to experiment with audio inputs that I want to try if I ever find a D model 614. I do my own car repairs so I need to get things done before the weather gets bad around here in the Albany, NY area. I guess they got smacked over on NE??

Here are the jacks added. I have not wired them as of this post but that will be next. I also did wire up the cable and was able to set the Mod Plate to 40 Mils. (had it closer to 100) I have to go over the whole circuit for the carbon mic situation. I will be using for line level audio input as in something from the computer to the speech amp to play recordings etc. The XLR is of course for the rack input of my choosing. Should be pretty trick. Now I see I am going to have to rig up some sort of other PTT. I am thinking foot switch and even a switch on the 614.   Also let me add I am going to give it a nice paint job this summer its just to cold for painting right now in Nevada.

Hello John, what are your plans now? It looks like you could go with line level perhaps by using the pot R-123?

I wonder if that transformer T-101 might be useful for anything in the circuit since it probably is low impedance? It would be great if it were 600 ohms! Maybe you could measure it? I did use a D-104 on one of the BC-614.s that I had and if I remember correctly, I changed the resistor R-101 from 1 meg to 5 meg.

What really surprised me one day while poking around in there that on V-101 that there was only about 17 volts B+ on the plate of the tube. I may have been mistaken about this voltage but it seems to stand out in my memory being that it was so low and worked perfectly!

Over

Not sure what I am doing yet. However I need to sort out how to properly key the thing using the 614.

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
W2PFY

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.

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  ;D ;D 
 

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. I’m 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 it’s 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

 

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.

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

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 3/16” 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). 

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

Thanks and have a great week,
Tom N5AMA

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

Looking forward to hearing that setup during this winter. 

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

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

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 

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

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 didn’t 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 I’ll 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 it’s sort of necessary. I do have an original manual for this rig and some of the illustrations are funny. I’m not sure if they are a result of our military or of the Hallicrafters group doing their thing but they are entertaining.

I’ll 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