Bob makes a good point. Indeed this was my first thought. However in my experience the 40m oscillation is a sustained event. The fact that the meter spike disappears when the VOX delay is set longer suggests to me that something else is going on. Key question: does it do it into a dummy load as well? The 40m oscillation *usually* only appears with a reactive load. I say usually because I had one that was so bad I was able to make it oscillate into a dummy, and also on 17m.

If you haven't yet, you need to buy a TinySA or TinySA Ultra. I have one of each. Fine toys, er, tools. Be sure to check the Wiki and buy from an approved seller. Bad clones abound. R&L in the USA is a good bet. DON'T buy from Amazon!

73

-Jim
NU0C

On Tue, 23 Apr 2024 17:35:45 +0000 (UTC)
"Bob Loving via groups.io" <bob.loving@...> wrote:

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.

--

73

-Jim
NU0C

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.

Look again. It's there, just easy to miss.

On Tue, 23 Apr 2024 03:43:03 -0700
"Jim VE7RF via groups.io" <jim.thom@...> wrote:

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

--

73

-Jim
NU0C

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

Very clear information, Jim. Thanks very much.
73 de Raoul CE3RY

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.

Images:

A view of the ALC board in my TR7 #1. The two small beads are original. The large one I added later just because I had one. This appears to be the forward wattmeter feed which would make sense.

Another view of a spare HPF/LPF module. Somewhat longer wires but not nearly as long as in #1 before I shortened them.

--

73

-Jim
NU0C

Hi Stan, thanks for the photo!? Can't really see the colors of the wires in your? picture but K6PO did verify what I suspected.

The first picture I posted had the BRN & BRN/BLK reversed.

Now if I could just find where I got that picture so I could correct it for whomever originally posted it!!
--

73/Rick

W4XA
*Every post is created using Linux

Excellent, Jim. Thanks!
73 de Raoul CE3RY

Image: shortened wires and ferrite beads between HPF and LPF.


--

73

-Jim
NU0C

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

Does this help?

73

Stan
KM4HQE

On Mon, Apr 22, 2024 at 03:50 PM, Paul K6PO wrote:

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

Hi Paul,


Thanks for the quick reply!!

Yours has the BRN and BRN/BLK the reverse of mine(which is wrong!)

I was to the point where I was going to open up my working L-4PS to see how it was wired!!?

Not sure where I found what I have in my picture.? Although I thought I got it from BAMA, when I looked at what they have,? none of the schematics there have any wiring color-codes shown on them. Must've found it somewhere else!

I discovered it when I started wiring up my rebuilt Hallicrafters Loudenboomer? (single 3-400/500) Power supply.

After I acquired an L-4PS plate transformer, I decided to dump the old Radio Industries INC full-wave (CT),? Mercury Rectifier, swinging-choke? stuff for the Drake style voltage doubler.

I'm going to run it on 120AC and will never use the low-voltage connections that Drake used for CW/TUNE

In fact, I'll probably also just hard wire my L-4B to stay in the SSB position since it's really no longer needed.

thanks again!


--

73/Rick

W4XA
*Every post is created using Linux

Many thanks Jim, I'll look in eBay to get some beads.?
73 de Raoul CE3RY

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

I will have another look later, as I have to open up a rig. The two HPF spares that I have did not have beads on the ALC board. I have found examples with beads on both ends of the red wire between the HPF and LPF, and another with a different wire beaded as well. I may have pictures somewhere.

As for the bead itself, 4A6 is the name of the bead that Drake commonly used. I researched it and the exact nature seems to be known only to Tektronix and the US government. But I did find some possible equivalents, and I purchased a some via eBay some 8 years ago that look exactly the same. So they must be the same, right? Kidding... Below is the sum total of the notes I took at the time. Don't ask me to explain any of it, it's been too long. :)
_____

4A6 bead.

E52-3N3Y-1G0 Krystinel Corp
111-00201-062 Amperex Electronic Corp
56-590-65/4A6 Amperex Electronic Corp
84127-35 Dla Land And Maritime
60-1037-03 Crane Electronics Inc.
84127-35 Defense Electronics Supply Center
Dla Land And Maritime
190SA168 Eaton Corporation, Eaton Motor Site
9170-0894 Agilent Technologies Inc., Hewlett Packard Co
FL0004F Scientific Radio Systems Inc
57-1634 Stackpole Corp The
276-0532-00 Tektronix Inc.
276-0532-00-BA Tektronix Inc.
276-532 Tektronix Inc.
5950-00-916-8080 Bae Systems Information And
British Sarozal Ltd
Bristol Electronics has 400 of Ferroxcube 56-590-65/4A6

Special Features: Ferrite; single thru hole 0.047 inch (1.19mm) dia.; 0.118 inch (2.997mm) lg; 0.138 inch (3.5mm) dia

FB43-101 Ferrite Bead

AL=600 +/- 20 %
OD = 0.138 in / 3.5 mm +/- 0.2 mm
ID = 0.051 in / 1.3 mm +/- 0.10 mm
HT= 0.128 in / 3.25 mm +/- 0.25 mm

RFI Suppression 5 - 500 MHz


_____

73

-Jim
NU0C



On Mon, 22 Apr 2024 13:54:26 -0700
"Raoul Meunier via groups.io" <rmeunier@...> wrote:

Beads have also been found on one of the wires connecting to the ALC board but I need to look at one to tell you which. A: Pending until I hear from you.

--

73

-Jim
NU0C

Wow! A lot of good information, thanks!

Jim, I'll reply based on your comments:

1. "Did you also add a ground strap at the other corner where there is an empty screw hole in the inner chassis wall?"? A:?Yes, that was something I had already done based on the information you provided some time ago in one of the threads.

2. "Also don't overlook the grounding of the ALC board. The two screws are a mechanical ground connection to the HPF module."? A:I did this a few days ago, not only cleaning the mating surfaces but adding star washers in between them on each side. This assures good connections.

3. ?"2^nd?Mixer shields over L701 and L703."?A:?The board in this TR7 does not have the shields. Fortunately, they are easy to make and install.

4. "Parasitic oscillation of the dual gate FET Q702 in the 2nd mixer board."? A: This is totally new to me. I will proceed based on the information from PA0TRT that you provided.

5. "For 10 Meters I have uploaded an Upconverter alignment tip from K8AC to the group Files section."? A:?I’m afraid I could not find the file. However, I have the information in my TR7 book, so I peak C418 for maximum power on 10m at the end of the Tx alignment.

6. *Very carefully* measure the base voltage of the drivers and finals in RX. It should be very close to zero volts. A: Done and ok.
   

7. "I don't know if this will be helpful or not but I noticed that in later version Drake shortened the wires between the HPF and LPF modules and added several ferrite beads. A: Both, the shortening of the wires and the beads, are pending.

8. Beads have also been found on one of the wires connecting to the ALC board but I need to look at one to tell you which. A: Pending until I hear from you.

I'll put my brain and hands to work to fix numbers 3, 4 and 7. Number 8 is pending.? For the beads I'll use what I have in my junk box; unfortunately, I have no idea of the material they are made of. This is becoming a compendium of information to fight the 40m oscillation. Certainly a keeper.

Thanks and until soon.
73 de Raoul CE3RY

?