BC-610 Questions

[W3GMS]

Hi Steve,

I have a model E as well and it worked very well when I bought it maybe 15 years ago.  Its in excellent condition and I look forward to getting it on the air from my new ham shack when it gets completed. 

I know many mod's are out there concerning hum with the BC-610 in relationship to the VFO tuning units.  I forget the details but the hum may have been FM onto the VFO stage.  Did you have any issues like that with yours.  I would prefer to use the original tuning units in mine and I have to believe that "issue" can be fixed.

73,
Joe, W3GMS 

[K3YA]

I just tuned my BC-610I up 160 Meters a few weeks ago and thought I would pass along a couple tidbits.

First, on 160M R9, the wire wound resistor in parallel with the 250TH plate choke runs VERY hot.  In my case it made a nasty burning smell as it cooked the adjacent bypass capacitor.  There is is a recommendation somewhere in the service manual to remove this resistor for operation below 2MHz and this is what I did.  I haven't tested the rig on 75 or 40 yet to see what if any effect this change has on higher band operation.

Second, I tuned up the transmitter with a 1.5-2 MHz output coil, but couldn't get sufficient coupling to the swinging link.  Then I put in a 2-3 MHz coil and the 50pF vacuum cap, which runs a significantly higher Q, and had plenty of coupling to the output link.   The higher Q of this set up probably reduces 2nd harmonic emissions quite a bit too.

C U on 160.
Charlie 

[Steve W8TOW]

Hi All, good BC-610 discussion. We could dedicate a complete sub-heading
to just BC-610's!

VFO FMing. A real problem with the rig is out of tolerance resistors
in the screen circuits of the exciter. To minimize this problem, check
all the screen dropping resistors in the 6L6 & 807 circuits. Additionally,
I found most of the component in the Tuning Units starting to drift out
of specs too. Since they are much easier to replace than any other components,
I'd swap them out too...once you do, you won't ever have to do it again!
If you really want to get away from FMing or frequency pulling, install
some good regulation for the LV, check out the 115 VAC power cord, and
your own house electrical circuits.
I have 15' distance from the TX to the electrical box; a 30A Circuit Breaker, and NOTHING
else on that side of the 120vac line to sag when I modulate.
Even said, I see my line voltage dip a few volts under modulation. Such
voltage variation contributes to stability issues in such old rigs with
marginal regulation.
If you really want to be serious, install a separate power supplies for the modulator...run
it off the other 120VAC line in your house....but this is overkill...
My solution: run it on crystals...or an external VFO with it's own PS!

As for the resistor in the Grid of the 250TH, R9. According to Skip, K7YOO, this component
need to be "bypassed" during 160m operation. The suggestion is to install a
knife switch next to it to bypass it. Another suggestion was to eliminate it
all together. I've not done this yet, but on the agenda next so I can
put my "E" on 160m, too.
If done, mount the knife switch so you can access it from the top of the
rig, or install a relay rather than a knife switch, allowing remote control if it
from an easily accessible toggle switch. (just don't drill a hole in the front panel!)

The best thing I've done to the rig was to install a 500pF cap in series to
ground off the rotating link.
The rig loads into 50 ohms nicely, and to put it on 160m, adding a 500pF fixed
cap in parallel, is easy!


73
Steve

[KM1H]

Back in 1959-60 while stationed at NAS Olathe, the K0NAB club station had a 610 that was just used as an amp for a 32V3 driver on 20 and 15M. Ive no idea what was done but it worked well into 6el Telrex's at 90/100'.

When that wasnt enough the big surplus amp with a pair of 1500T's modulated by 1000T's were driven by the 610. I dont remember the military designation but it was in 2 tall racks and with a MG set providing voltages. I enjoyed watching it in operation!

Carl

[WQ9E]

There was a note in Electric Radio about the source of hum, I think I stuck it in my folder of BC-610 stuff.  If someone else doesn't post a synopsis first I will dig it out this weekend.

I have a 610D and I have been OK using the oscillator in the tuning units thus far but I haven't had mine on the air in several months.  I decided it had to have a SX-28 paired with it and that turned into a restoration of a second SX-28 along with other projects.

[K5UJ]

Check ER 69, 126, 127, 128, and 129.
Also 136, 139, 185, 186

Rob