The BC-610-E has landed

[W2VW]

FMing isn't a problem, it's an undocumented feature 

Be the only folks on the air whose tx can be identified quickly by experienced people hearing the AM and FM fade differently during QSB.

[N8ETQ]

   Really???  They don't call it the "Voice of Victory" for nuthin'

/Dan

FMing isn't a problem, it's an undocumented feature 

Be the only folks on the air whose tx can be identified quickly by experienced people hearing the AM and FM fade differently during QSB.

[N6YW]

We have audio! 
The speech amp works without any noticeable hum. The relay modulates my voice, so that mod will be done. Not sure if I'm getting 100% modulation although I will hook up my SB-610 scope in order to find out. All of this is being done outside in the back yard, so it's a lashup right now but still, exciting to see this process taking shape. The D-104 works like a charm so far.
More to follow.

[W2VW]

The 610 makes a fine business bug zapper.

[flintstone mop]

We have audio! 
The speech amp works without any noticeable hum. The relay modulates my voice, so that mod will be done. Not sure if I'm getting 100% modulation although I will hook up my SB-610 scope in order to find out. All of this is being done outside in the back yard, so it's a lashup right now but still, exciting to see this process taking shape. The D-104 works like a charm so far.
More to follow.

You are a LEFT COASTER......and it is nice wx.

[N6YW]

Well... someone needs good wx om. 

[N6YW]

Update:
I hooked up the SB-610 scope to test the speech amp and it appears I have 100% modulation
using a D-104. I listened with a receiver and I think it's buzzard enough to put on the air for
Christmas. There is room for improvement but for now it will suffice.
Back to work.

[W6DRZ]

Looking forward to hearing it on 3870 one of these nights.

Craig

[N6YW]

@Dan:
" Put a 2 - 10 Mf cap across the overload relay coil to
keep it from buzzing with modulation. 200V job will do,
if it blows it blows, keep that little box over it."

You're referring to RY5, correct?
The photo shows a 10uf/500 volt lytic across RY5 but I had to nestle it next to RY2 to make it fit.
I used flying leads soldered to the lytic leads insulated with shrink tubing. The gas seal is pointed towards the box end should it acquire the need to excuse it's contents. Positive polarity to the transformer CT.

[N6YW]

I am posting some photos of the innerds, and of particular interest is the "Hanging Chad" resistor from one of the regulator tubes on the top deck. There are also two leads on the bottom right power supply deck that have been taped off for some reason and evidently, a long time ago.
I added a better shot underneath the RF section. See bottom photo.
The beat goes on...

[N6YW]

Power supply leads taped off...
Curious to say the least.

[N6YW]

I did more testing this afternoon but this time into an antenna and monitoring with a Flex 5000A. The RF Applications 5000P wattmeter shows 275 watts of carrier @225ma into 50 ohms, and peaking at only 578 watts PEP. From this, I gather I am not achieving the goal of good modulation, and while it sounds good audio wise, it is not a happenin thing. So, I need some guidance here from some of you sages of AM.
I will test the tubes in the speech amp and modulator driver stages. Is there anything else I should consider? I put in new 6V6 & 6L6 tubes and I am seeing less carrier than with the old stock tubes. I was also using the Eico 722 VFO instead of the crystal. This will be reversed tomorrow to see if it makes any noticeable difference in carrier level.
The capacitor mod for the plate protect relay seemed to work, although It might need more than the 10uf I used. Every once in awhile on voice peaks I detected a little talkback but not much.
Getting this thing to really modulate is my focus now. Christmas is just around the corner and I need to make a good presentation.   I will also see if a dynamic mic drives the audio better.
Billy N6YW

[N8ETQ]

   Hey Billy,


      Glad to hear your making headway on your 610!  Your way ahead of
me right now.  Snow removal and Vehicle Maint. (Not mine of course)
have been kickin' my but!


"The RF Applications 5000P wattmeter shows 275 watts of carrier @225ma into 50 ohms, and peaking at only 578 watts PEP"

      A couple of things here you may want to try.  The BC-614-E has
a limiter circuit built in, I know you mentioned yours was modified
but It may be helpful to determine if it is still in circuit by
trying it. I don't recall which way the pot needs to go to shut it
off but your scope will show you the way.

      You could also try to reverse the audio phasing with respect
to your mic.  Most easily accomplished by cross connecting the grid
lines at the 100TH's and see if that doesn't buy you something.


"The capacitor mod for the plate protect relay seemed to work, although It might need more than the 10uf I used."

      It may need a bit more but could also be the Iron. Mine makes
a lot of "Rucouse" on voice peaks too.  Make sure it's bolted down good.


"I will also see if a dynamic mic drives the audio better."

      I bet it will, wonder if you ever got the color off the 100TH
plates?  Whats your resting Ip on the Mod I meter?


      Keep up the good work Billy, wind chill's below 0 F here today
so I may get a chance to play...  73 for now OM, I'll take a few pics
today if I get into Mine.

/Dan

[W2VW]

How much final grid current does it have?

[N8ETQ]

How much final grid current does it have?

   Good Point!

[N2DTS]

Grid drive and modulator swing are needed to get high modulation, plus the correct phazing and plenty of of audio drive to the modulator grids.

I always like a lot of extra grid drive, and I never burned up a grid...

[N6YW]

Thank you for the replies. I will address each of them.
I am curious if interfacing my Eico 730 modulator would be a better work around in considering the possibility of the speech amp needing more in depth attention.
As to the limiter control, I am not sure but will see if it is even in the circuit.
I'm going to test the tubes today and give the audio paths inside of the speech amp a good going over to see what was done prior to me. I think all of this is my being a newbie and a cumulative assortment of minor technical issues with the system. This is the meat and potatoes of the learning curve I enjoy the most. Thanks again!
Onward....
Billy

[N8ETQ]

   Brought my 610 above room temperature today!



   All went pretty well, after first plugging it in to
his dedicated 120V outlet.  No surprises after about
3 years of non-use. More of a re-learning thing for
me. Only problem is NO Audio. Damn...

   I'll get that sorted out this week, The older 610's
A-D had a "VU" meter in the speech amp and the Mod I
meter was internal to the 610, on one of the side wings,
the Antenna I meter was in the other side wing.  With
the WWII meter shortage the "VU" meter was done away
with and the Antenna I meter was moved to the BC-939.
The Modulator Plate meter was moved to the BC-614.
So right now I can set the resting Mod current to 30ma
but it won't pass audio. Not sure if it's getting out
of the BC-614. I tried 2 mics, one the original T-50
and the other my Condenser job with the Phantom power
provided by an ART 12AX7 "Black Box" that does have
a meter on it and the condenser mic works. The T-50
was known to work a few years ago, and I was told it
even sounded pretty good.

   I did a little Trouble shooting but NO Joy so far.
I think I'll pair this up a nice BC-779-B (SP-200 ish)
for the RX.

Just an update for Billy.

73

/Dan


Pix of the meters at about 250W to the B&W Match Master.
(ME-165 ?? was that it?)

[W2PFY]

Someday you may hear a loud bang from the 614. It will be those two caps that are on the primary of the power transformer. I just clipped them out with no ill effect whatsoever. There is another one on the output socket that goes to the 610. When that one shorts out, your transmitter HV will be keyed as soon as you turn on the transmitter. Clip that one out too.

I also installed a large value cap from the wiper arm of the bias pot to ground. I think I used something like 50,000 mf. I also ran a wire off the negative terminal of the cap out to the back of the 610  so I could use this bias point to run a backwards hooked up audio transformer to drive the grids directly. All but the purists say it sounds good doing it this way.

Attached is an audio clip of my BC-610D driving the grids with an audio transformer.

[N6YW]

Terry & all.
Thanks for the replies.
I will look to see if those caps are still installed Terry.
To answer some earlier questions, the modulator bias is set to 40ma resting current.
I will have to check to see what kind of grid swing I am getting from the PA. My setup
here in the backyard is a bit of a hassle, with the BC-614 cable stretched close to my
shop where I could use the microphone, see my shop RF meters and monitor the audio
via my Flex 5000A powered monitor speaker. I am now getting 315 watts of carrier,
but only getting 690 watts peak output. All the tubes in the 614 audio path are fine.
I am thinking that perhaps the 2A3's might be a bit tired, although I have not checked
them. I am considering using my Eico 730 Audio Modulator. It has a multi-match output
transformer and the 50 watts of audio is beautiful sounding. Does anyone have any suggestions
regarding the use of the 730? If my 2A3's are weak, or if one of the interstage coupling
transformers have become compromised. The 100TH's might be suspect as well, not sure at this point.
I tried swapping phase of the modulator grids and no gain at all. Also, it behaved a little eratic today
that caused the transmitter to not produce audio of any kind. It went into protect mode also, which necessitated my cycling the transmitter on and off. So, I believe I need to do a thorough cleaning, including the relay contacts and tighten down every nut/wire connection and secure all ground returns.
I noticed some of the leads were a little loose. I have several feet of 15KV high tension lead (silicone) that would be a good candidate for replacing all of the old HT leads.
My intent is to get this box working as stock as possible without resorting to a myriad of mods. I am not a purist, but reasoning for sound operation is key to my goals. If something sucks, in the dumper it goes. Right now, I have the 614 back on the bench for some tests and checks. The limiter is absolutely out of the audio path, including the tube. I will keep the group posted.
Thanks again

[N6YW]

BC-614 update:
Finished the cleanup and rejuvenation of the audio path. I now have real high quality, fresh manufactured Mallory 150 series .1 caps in the coupling stages of the 1st & 2nd audio amps, and the phase inverter
got the primo STK .047 caps into the audio driver output. The bypass caps for the PI were replaced as well. I have some reading to do tonight regarding the PTT circuit. The two way toggle switch is busted and I need to replace it, but while I am at it, I would rather have the PTT controlled at the mic connector as well. Not sure if there is high voltage present on the key line.
All of the resistors check good, but the real deal will be checking voltages, tomorrow. From there, it's the cleaning crew and audio path check of the modulator deck. I am almost of the mind to take the entire transmitter apart, deck by deck in order to really scope things out but now is not the time. The rearrangement of the shop/shack has to occur first. My body says no way
If I could only shut my mind off...

[N2DTS]

This is the fun part, you learn a lot and get to know your rig.
Otherwise, you just talk into it, what fun is that?

[N6YW]

The modifications to the speech amp made a remarkable improvement in quality, but did little to gain any additional modulation. With the transmitter keyed @250 ma plate current, I am getting 60 ma of grid current, but with modulation, the swing is only slightly higher. So, I am not getting enough drive at all.
Any ideas where I should begin? My feeling lies in the driver transformer prior to the 2A3's or afterwards.
I shall test the 2A3's today to see if they're up to the task. Working in the back yard has it's limits let me tell ya!  
Will check DC resistance of T7 & T8.

[W2PFY]

I am getting 60 ma of grid current, but with modulation, the swing is only slightly higher. So, I am not getting enough drive at all.
Any ideas where I should begin?

What band are you using to test on? On 160-75 you should see as much as 100 ma. On 40 about 70 ma and on 20 about 60 ma. Check you screen grid resistors on the 807 tubes. IIRC they are 22 K . If they are bad, be sure to use at least one watt resistors or you will be going back in to replace them at a later date. The other thing you can do is replace the rectifier tube on the RF deck with a solid state device. It will make a big difference. I do not recommend solid stating the mod deck rectifier. You may have a soft 250TH. If you have another, try it and see what your grid drive is? If you are getting downward modulation, that is another sign that the tube is weak. I am no expert on 610 but I have been using two, A "C" model and now  "D" model for the past thirty years and have had the top off both over thirty times. This is how I check my 100TH tubes. Set the bias so that the tubes are drawing 100 mills. Both plates should have the same red glow. If one is less red than the other, it is the weaker tube. Replace it and things will improve.

On your Eico mod. Does it have a 500 ohm output? If so, you can get an audio transformer with a 500 ohm tap on it and reverse connect it to drive the grids. The secondary should be about 3 K PP. You should also load the secondary with resistors from each PP terminal to center tap to keep the transformer from looking into an infinite load.

I have also found that the tuning units will varies by manufacture where one will provide more drive than another. That could be a problem with components but it also may have been some update that we are not aware of. One other question that really makes no difference as far as trouble shooting gos but I am curious about what kind of dummy load you are using?

[N6YW]

Terry
Testing on 75 meters.
Thank you for the reply and I will check those items off the list and report back. The driver transformer in the BC-614 tests fine, and so does the primary of T7 which goes to the 2A3's.
Onward!