BC-614 Mods

[n9ami]

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?

[W2PFY]

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

[n9ami]

Thanks Terry,
  It is the I model.

John

[pa3hco]

with this mods work the bc614 better

[n9ami]

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

[W2PFY]

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 . 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/

[n9ami]

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.

[n9ami]

Modified photo with circles as described in my last post.

[W2PFY]

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?

[n9ami]

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. 

[W2PFY]

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 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

[n9ami]

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.

[W2PFY]

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

[n9ami]

I was tracing the single white wire you asked about.

[n9ami]

I was tracing the single white wire you asked about.

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

[W2PFY]

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

[n9ami]

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

[W2PFY]

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

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

[n9ami]

Alright good deal. I will snip that out.

[n9ami]

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.

[W2PFY]

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?

[n9ami]

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

[W2PFY]

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??

[n9ami]

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.

[W2PFY]

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