BC-610 and CW

[Rick K5IAR]

I have never used the BC-610 on CW, is there anything in particular I need to do or watch for that wasn't done in fone mode?  I am thinking about putting the "H" model on fone and dedicating the "E" model to CW since I have such a time with talk back from the modulation transformer.  Any hints or advice will be appreciated...

Rick/K5IAR

[KB2WIG]

Have you considered moving the mod transformer out of the box and somehow damping the sound?    klc

[Rick K5IAR]

No, I have never considered moving the iron out of the cabinet, but I have tried many things to reduce the feedback.  The best results were achieved when I tightened all the bolts on the transformer, but it is still not acceptable.  I have to have the box relatively close to the operating position (about 3 feet), so it's all but impossible to get more than 85% modulation without causing feedback.  The ideal solution would be use one of the later model BC-610 modulation trannys that are potted.  If it will perform good as a CW transmitter, which I think it will, I'll just use the "H" for fone, there is no talk back problem at all with it.

Thanks for the reply...
Rick/K5IAR

[AB2EZ]

Rick

I solved the talk back/feedback problem on my KW-1 by removing the bolts that hold the mod transformer to its chassis, and placing a computer mouse pad under the transformer.

Best regards
Stu
AB2EZ

[k4kyv]

Before you give up on the BC-610E, it may not be the mod transformer that is talking back.  Unless you already have the modification installed, the noise is more  likely the overload relay chattering due to the modulated PA plate current passing through it.

To cure the problem, place a 100 mfd or so electrolytic capacitor from the midtap of the plate transformer (accessible with the rear cover removed in the E-model) to ground.  The positive side should go to ground, and the negative side to the midtap.  That should cure 90% of the problem by bypassing the audio around the relay coil, without affecting the performance of the O/L relay.  Just be sure to use a good quality cap.  It needs only be rated for 50 volts or so.

[Rick K5IAR]

Thanks Don, Stu and all...

Unfortunately, I have tried all of the methods mentioned with little or no success.  The relay was the first thing I did and I just knew that was going to solve it, but it made no difference.  I mounted the modulation transformer on rubber cushions and did get a little help, but not enough to really help.  The feedback is occurring from the windings and laminations of the mod iron and the chassis was amplifying it a little, but not that much.  I sure appreciate the suggestions.  It is actually a little more transmitter than I need for CW as I usually don't run over 100 watts in that mode.  Most guys I have talked to with the "E" have had similar problems and say to get as far away from it as possible and forget it.    

Thanks guys... keep'em comin'...

Rick/K5IAR

[Rick K5IAR]

Real estate is at a premium under the hood of these old gals.  Maybe someday I'll run across another modulation tranny that will fill the bill.  I really like the looks of the old one, but...  I have an "I" model also, well, kind of, it is in pieces, but I think they are all here except, of course, the mod tranny!  Thanks Mack and all...

Rick/K5IAR

[WBear2GCR]

My suggestion is like what N4VJB said:


Pull tranny.
Remove end bells.
Place fresh bolts through the holes in the lams and tighten nuts.
Mark wires with strips of tape (1,2,3 strips etc.) Make note of what goes where.
Take to motor rewind shop, let them dip it.

Alternatively: find a big pressure cooker that will fit the core without the endbells on.
place insulating varnish (bought from appropriate supply company) in pressure cooker, after doing the above prep. Suck air out using the input side of ur air compressor, or other suitable pump - this drives the air out of the inside of the tranny and fills it with varnish. Remove from pressure cooker (you probably wanted to hook up a heavy wire for that before you started, or lifts off the bolts?). Bake in oven at low temp for an hour or too. Repaint outside of lams w/black lacquer. Reassemble.

Probably will be dead quiet now.

Can always go for two applications.

The vacuum method is superior to the basic dip.

Just a thought.

           _-_-bear

Alternative 2, you might be able to find a company that does vacuum dipping and get them to drop your unit in their tank for a few buck$.

[Rick K5IAR]

Thanks Bear...   I'm wondering if when I take the bolts out of the core so I can install the end bells will it possible loosen the varnish?  I have never done anything like that, so I am totally uninformed.

Rick/K5IAR

[WBear2GCR]

Rick,

Assuming you put bolts in when you do the dip, the core will still be compressed at it's final position. The varnish or other potting material will penetrate and fill the open spaces in the windings. It's a thin coat usually, that's why I suggested doing it twice.

The varnish is pretty tough, and I doubt that taking the bolts out will have any effect at all. The main goal is to keep the windings in place with respect to each other. The minor gaps in the lams may also get filled, that is really thin and the varnish acts like a glue there.

You can also use "tar" or "wax" btw. Tar is often found in potted iron, as is "wax". The wax will work, but tends to drip when the windings get hot. Not so bad in a sealed can... both require that the stuff gets heated to install. The advantage to them is that they do come apart like they went together, which in some situations turns out to be an advantage, but not much of one, imho.

I've never done it myself either, but have seen that others have done it.

I'd take an unimportant bit of iron and try it out first on that, before committing to the real thing. Get the process working right first.

Btw, afaik the "tar" is the same as the hot liquid the pavers use to seal cracks in the pavement. Someone else can check me out on that one...

                          _-_-bear

[k7yoo]

You are on the right track with vacuum impregnation of the transformer. You don't need to trash a pressure cooker to do it though--most motor rewind shops have the equipment to do it. Winona is a small town (30K) and the motor shop 4 blocks from my house does it all the time.
Skip

[Rick K5IAR]

Thanks guys, this is some great information.  I bet Gary, WZ1M, could do that for me.

Rick/K5IAR

[WBear2GCR]

Are you guys sure that the varnish tank is vacuum?

The local, very large industrial motor shop in this area does not do vacuum at all.
I was dissapointed to find that out.

Their varnish is red opaque and rather thin watery stuff, btw.

             _-_-bear

[The Slab Bacon]

Bear, It wuz good hearing you on saturday night!!

The red insulating "varnish" IIRC iz called "Glyptal" or something like that. We used to use to coat the insides of racing engines years ago to promote faster oil drainage back to the pan. (Until we found that it would flake off and clog up the oil pump screens).

what I often do as an insurence policy to impregnate old transfoma windings iz pretty simple. First I remove the end bells (covers) then I bake it at a low temp like 190-200 deg for 8-12 hours. (this will open it up a little and hopefully expel any trapped moisture) Then while it is hot, fresh out of the oven, I drop it into a bucket full of oil based varnish to cool. Afta it cools to room temp, I pull it out out of the bucket to air dry over night. I then will dunk it a few more times at room temp and let it dry until it formz a nice "glaze" on it kinda like a "honey dipped" or glazed doughnut. I then let it set in a warm, dry place for a few weekz (or longer if possible) to dry thoroughly. I have neva had one fail like this. It is also good for bringing back transfomas that have been subjected to questionable storage.

I heard this from some old buzzard many years ago and have been doing it evva since. The trick of it all is dropping the still hot transfoma into the bucket of varnish to cool. The heat thins out the varnish and the contraction ov cooling draws it into the windingz and laminationz. I have done this to transfomas, generator and mota armatures, and magneto coilz for many yearz.

                                               The Slab Bacon

[The Slab Bacon]

Datz 'cause you wuz runnin those chebbies!! I used to feel that chebbies were like that certain part of the anatomy, you know, "everybody has one".

I used to prefet chizzler productz!! I built a long string ov fast 340s and 383s and even fasta 440s. I used to turn .060 ova 440s well ova 7000 and neva had one come apart!!  Now clutches, transmixerz and drive shaftz were anotha story!!

                                                 The Slab Bacon

[The Slab Bacon]

I did a lot of research back in those days. I spent a kings ransom on long distance fone calls (before the days of calling packages) with Larry Sheppard and the guys at Chrysler, as well as the tech staff at General Kinetics cams. I wtill have tons of looseleaf materials stored away in the attic from that correspondance close to 30 years ago.

We worked out the right combination of "goodies" and machine work to haul a 3700+lb car 10.90s @120+ with a 440. I still have the recipe just in case I ever want to build anotha. I even have the cam card and lobe profiles so I can have anyone grind that cam for me. But ur right the stock heads and cam run outa breath around 5500. Mine had no problems pulling hard way past 7000.

A 1967 427 camode was a very formidable piece of iron to reckon with. Big engine, big horsepower, and only weighed around 2800-2900lb. I know someone who has an original '68 or 9 427 camode, it has never had tags on it. It has been a race car since the day it wuz bought new!! (It didnt even have a heater or radio in it)

                                                 The Slab Bacon

[The Slab Bacon]

(boy did we get off topic here!!)

It may have well been. We never payed much attention to stuf like that back then. the shame of it all is that I welded a 6 point cage and frame connectors in it 30 years ago. Back "when it wasent worth anything". I also still know of 2 1971 Plymouth Dustbags that have been racecars their whole lives. Both have less than 1K on the odometers.

The one that got away was Jack Arnew's 1970 Hemi 'Cuda convertible that spent its whole life as a SS/EA racer. At todays Barrett -Jackson auction prices its just plain "Priceless"!!

COPOs, Joel Rosen's Motion cars, Chrysler factory hemi cars, Ford's unique Boss packages. Life wuz good back then!!

Who'd ov eva thunk back then what it would be worth now!!

                                             The Slab Bacon