One owner TR7 station available in Nashville, TN. $1500 for all of it, will
ship with insurance at buyer's expense, not interested in trades, serious
offers seriously considered. All the items work properly; only possible
exception would possibly be the phone patch as it hasn't been utilized in
quite a number of years. Please contact me directly with any questions; I'm
good on QRZ.

TR7 transceiver (model 1337), just back from service by Ron Baker WB4HFN;
details attached
MS7 speaker
RV7 remote VFO
PS7 power supply
P75 phone patch
Also included are the original boxes for the TR7 & the PS7, a small parts
cabinet with extender cards & other Drake bits & pieces.
Photos here:

Thanks,
Robin Midgett K4IDC

Steve, is this action noted on all bands? Or only one, namely 40M?
The oscillation on 40M occurs up in the 9- to 10-MHz range so the TX LPF may attenuate the signal sufficiently to not indicate on a Wattmeter. Use a spectrum analyzer to "sniff" with a loop in the LPF section while this is happening.?
SAs aren't as expensive as in the old days. Even the "Tinysa Spectrum Analyzer" is available for $60-$70 on Amazon and will do your cooking proud.
73,Bob K9JU
Maryville, TN

On Tuesday, April 23, 2024 at 12:30:53 PM EDT, Jim Shorney <jimnu0c@...> wrote:


Find out where the meter spike voltage is coming from. If it is from the wattmeter sensor you may have a parasitic oscillation. If it is coming from the 2nd IF/Audio board there may be a timing issue. Which version board do you have? If it is a real TR7A you should have version 2, which has all the fixes. But with board swapping and "A" version fakery you never know for sure unless you look. The version 1 IF/Audio board had some problems that were fixed by factory mods. Very old boards in the field may not have all of the mods. Check the values of R1186 and R1187. The schematics say 10K but I have seen values as low as 1.5K in the real world. Lower values will reduce the T/R turnaround time. You might also check C1151.

How does your CW look? The CW generator is a crystal circuit on the IF/Audio board. It is a bit finicky to get right as Floyd K8AC found out. See his article about TR7 key clicks on HFN.

The VOX and T/R control magic happen on the TX Exciter board. You may want to check for marginal electrolytics there. Also check the +10T and +10R for proper switching. It should be a reasonably fast transition between +10 and zero.

73

-Jim
NU0C

On Tue, 23 Apr 2024 13:40:58 +0000
"Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote:

Whilst we are in discussions over wattmeter readings and so on, I’ve had a chronic anomaly with my TR7A and its wattmeter in CW mode.

When I transmit on CW, upon release of the key, the meter swings to the right peg. Then we have normal readings. During the time that the meter indicates maximum, there is no RF at the antenna connection (verified with external wattmeter and with a scope).

This happens only in CW, with the VOX delay set to minimum or near minimum. If I bring the delay out to around 1 second, everything looks normal. It occurs on all bands. There’s no indication in SSB or AM.

Could I be looking at a sticky relay? I don’t have a spare to swap, at the moment.

73,

Steve Wedge, W1ES/4

Time flies like an arrow. Fruit flies like a banana.

Whilst we are in discussions over wattmeter readings and so on, I’ve had a chronic anomaly with my TR7A and its wattmeter in CW mode.

When I transmit on CW, upon release of the key, the meter swings to the right peg. Then we have normal readings. During the time that the meter indicates maximum, there is no RF at the antenna connection (verified with external wattmeter and with a scope).

This happens only in CW, with the VOX delay set to minimum or near minimum. If I bring the delay out to around 1 second, everything looks normal. It occurs on all bands. There’s no indication in SSB or AM.

Could I be looking at a sticky relay? I don’t have a spare to swap, at the moment.

73,

Steve Wedge, W1ES/4

Time flies like an arrow. Fruit flies like a banana.

The schematic only depicts one 15 amp breaker, when in fact there are 2 of em.

The following files and folders have been uploaded to the Files area of the [email protected] group.

• /Drake_TR-7 Static Arrestor Installation.pdf

By: Jim Shorney <jimNU0C@...>

Description:
TR7 Static Arrestor Installation. This was standard equipment in later TR7s and a a service update for rigs sent in for repair. This document is the instruction for end-user installation. The static arrestor is a CG90L gas discharge device.

73/Rick

I got kind of busy last week. ?In replacing R3 in the AC-4, I decided to isolate C3 and C4 from the circuit and use a DC PS to condition both of these electrolytic capacitors, starting with a resistance measurement with the VTVM (1.5 VDC); individually, within 30 minutes they were up to 50 Mohm. ?Then overnight, they were up to 150 Mohm and climbing. ?I noticed C4b would drop a little to 75 Mohm then increase back to 150 Mohm; I interpret this as a clump of non-ionized electrolyte being uncovered and taking ?time to ionize the solution with a consistent open dielectric gap; nice that all of that is automatic, just applying a potential difference with the correct polarity. ?C4b had not been conditioned otherwise, all others had been. ?This AC-4 appeared to be completely factory with their practice of laying a component lead or wire against a terminal, then applying A LOT of solder; no good mechanical joint was created before soldering. ?Solder must have been really cheap then. ?The good part was it was really easy to unsolder all the connections. ?C4 was found to be a shiny aluminum can with C4b a 100 uF in lieu of 80 uF. ?The rest of the electrolytics were covered with canary yellow cardboard: all Mallory. ?C5 a and b were found to be 40 uF in lieu of 20 uF.
Leakage current measured for C3 and C4 follows.
C4a: 3.4 uADC constant. ?Capacitance measured 122.5 uF.
C4b: 4.1-4.4 uADC hopping around. ?Capacitance measured 124.2 uF.
C3: 3.4 uADC. ?Capacitance measured 121.8 uF.

With these caps about 20% greater than nominal capacitance ?(nothing surprising), the average DC voltage rises a little higher due to longer RC time constant of the RC filters.
Ambient temperature for slow conditioning up to rated WVDC was 78 deg F; the base of the can was a few degrees higher (handy IR thermometer).
With input voltage set to 120 VRMS, the following UNLOADED outputs were as follows.
650 VDC nominal, 720 VDC measured.
250 VDC nominal, 295 VDC measured.
BIAS -46.5 to -100 VDC, steady.
Filament voltage measured 14.87 VRMS.

I expect all these voltages will decrease much closer to nominal when loaded with the transceiver or transmitter. ?I also expect a significant rise in input line voltage will produce a significant rise in output voltages, loaded or unloaded. ?Probably the best thing to do is use an auto-transformer with the AC-4, as these are clearly unregulated power supplies. ?

I’m cleaning up and repairing a DC-4. ?The input voltage must be 12.6 VDC, as 13.8 VDC has shown to produce much higher than desired output voltages, with little to no sagging of 12.6 VDC filament voltage. ?Perhaps an AC-DC switching power supply, and the DC-DC power supply (DC-4) is a better solution in order to regulate the input voltages to these radios. ?Using late technology, modest priced good quality and noise-free switchers that adjust to 12.6 volts DC are available. ?I’m going to investigate this scheme. ?There are many attributes to using this power supply scheme.

One other note: A sign of a good functioning electrolytic capacitor is observed after conditioning, or regular use. ?With the capacitor isolated from circuit, discharge the cap with a homemade shorting probe and approximately 10 kohm resistor in series (keeps the v= Ldi/dt air breakdown sparks from occurring). ?Count to 20 connected to the cap. Have your voltmeter with lower voltage scale ready and attach it to the leads immediately after removing the shorting probe. ?The DC ?voltage should immediately and continually rise from zero on its own to some value being a reasonable percentage of the rated working voltage. ?A fast rate of immediate rise indicates you should EXPECT it to be in good operating condition.

73,
Michael, N4KZO

开云体育

Here's what I have in my files:?
--
73, Paul K6PO

73/Rick