There are Drake noise blankers and then all the rest. I agree on the NB-7. This
also applies to the noise blankers used in the TR-4 series including the TR-6
and the R-4C, SPR-4 receivers. Although the R-4B has a decent noise blanker, it
is nowhere near as effective as the ones just mentioned.
The 723 regulator is probably bad. One way to confirm this is by measuring the
voltage on pins 5 and 6 which should be around 7.1 volts. The 723 is powered
separately from the main supply by its own DC source. There is a 2N3566 pass
transistor supplying DC to pins 11 and 12. The base of this
None. The best way to find out if a 6JB6 is good or not is by direct
substitution. Sweep tubes were never meant for RF PA use. Tube testers, except
for the Hickok brand usually test for tube parameters at 120 Hz or in your
case, maybe 100 Hz, not Mhz. Hickok, I believe used 5 kHz for tube
Very interesting post. Suddenly I realize there is another fly in the ointment
besides part and hardware obsolescence: the operating system. I wonder what
Drake used. Was it Dos, CP/M, or what? Also what is the data format? Im curious.
-- Original message --
From: Jim
I thought this would be obvious just from looking at the final cage: there is
no room. The layout and size of the TR-4 final stage is quite different from
the T-4X series. As far as dimensions go, they are both the same height but
that's it. T-4X/TR-4: width= 6 1/2 vs 6 3/4, depth: 4 1/2 vs 5
An open 220k bleeder resistor makes sense. I guess you could check that by
disconnecting it and checking the resistance. Makes me wonder what would cause
it to fail. Assuming 250 volts it would need to dissipate 0.28 watt. If it's a
1/2 watt carbon composition resistor, it might have increased
It sounds like the carrier frequency is not centered in the middle of the two
filters.
-- Original message --
From: Robert Ladden [EMAIL PROTECTED]
Robert Ladden made an utterance to the drakelist gang
Not to mention that those are single turn pots too. I replaced mine with 10
turn trimpots a while ago.
-- Original message --
From: Jim Shorney [EMAIL PROTECTED]
Jim Shorney made an utterance to the drakelist gang
What is RG75? what are its characteristics? The only RG-75 I know of was a type
of rectangular waveguide for microwave. There must be another factor causing
your problem. Please don't take this personally as I've experienced all the
problems I'm about to list. Poor soldering, inner conductor
Sartori was a consulting engineer at Texas Instruments when he wrote the
article. In those days it was possible to have a semiconductor company
manufacture custom devices on a small lot or sample basis. Therefore, he had
access to a gold mine of resources few others had. However, custom devices
That was also part of the old Marine band. There used to be lots of interesting ttraffic there in the old days. Some was AM and the rest USB commercial radiotelephone. Not much there now.
-- Original message -- From: Garey Barrell [EMAIL PROTECTED] Garey Barrell <[EMAIL
The TR-4 and T-4 share the same "type" of AM, not the same circuitry.However the 13DE7 does supply screen voltage to the finals so a bad one could be the problem.Getting back to the TR-4 in need of troubleshooting: does it work on CW as well as SSB? The carrier shift of +1kHz is the same for AM
Hopefully, for your sake, the passband tuning unit is not in need of alignment. I doubt very much that bad caps are to blame for your troubles that is unless you can see that some or one of them has broken off a piece. However, there are switch contacts involved in the assembly so there is a
There are a couple ofadvantagesin using several small caps in parallel over a single large cap.First, equivalent series resistance is decreased and second, equivalent series inductance is likewise reduced. We do this all the time in designing DC/DC converters. Also, don't overlook the fact that
[EMAIL PROTECTED] made an utterence to the drakelist gang
--
Regardless of which type of filament it is the fact is that filament
voltage is critical for maximizing tube life. Too little is probably worse
than too much. You can
[EMAIL PROTECTED] made an utterence to the drakelist gang
--
For those interested in the QST construction article, I have some info on
parts substitutions from the author as well as myself.
1) The VFD at Digi-Key is no-longer
I wonder if like me, a number of people have found out some of the vital
components mentioned in the article are unobtanium. For example, the
encoder. I think I found a usable though not exact substitute at Digi-Key,
part number GH3073-ND. The VFD display is another. Again a substitute
might be
Of 3 AC-4 power supplies I own, one has always had excessive hum. The
previous owner told me he tried to replace the negative bias filter cap to
no avail. After looking inside, the only difference I could find was the
troublesome supply had much smaller interconnecting wires from the supply
to
I think I paid around $12.00 each some three years ago at JAN Crystals.
I'm sure it costs more by now. The neat thing is they have the crystal
specs on hand and you only have to say it's for a Drake (fill in the model
number). Unfortunately you have to wait 3 - 4 weeks for delivery. On the
other
Drake front panels are not painted, they're anodized.
The paint used on Drake front panels is pretty fragile. I'd not
try any harsh cleaners... creme hand cleaner is gentle enough, and I've
tried it with Drake gear with success. I'd not try Windex/Fantastik or
other harsher chems... the
All the transformers in my R-4 receivers get hot to the touch under normal
conditions. However, the presence of 5.2 volts of ripple indicates you may
have other problems that don't necessarily point to a bad cap. Could be a
power supply diode is bad or a tube is drawing excessive current. In the
The sky is not falling. I think we should get our facts straight before
running off cliffs. The email tax story was an idea put forth by the
United Nations to help undeveloped nations with revenues. Their words
and ideas, not mine. So it has nothing to do with the US. Furthermore, the
UN has
CORRECTION: The B line does not have 4 pole crystal filters built-in. It
has as single 8kHz (more or less)crystal filter in the front end. The
bandwidths in the R-4/A/B is provided by a single L/C filter arrangement
through switching of coupling and padding capacitors to increase or
increase
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