Thanks, Jim. I see the plate. Couldn't I just mount my box fan on the top
cover right where that plate is? It already has an AC power cord.

joseph n. graif
k4jng

....except for the Tantalum capacitors. If they are not shorted or burned leave them alone.

73

-Jim
NU0C

On Mon, 29 Jan 2024 14:32:45 -0600
"Jim Shorney via groups.io" <jimNU0C@...> wrote:

Don't spend a lot of time testing the caps. They are all old. Just replace them.

--

73

-Jim
NU0C

The RV75 does seem to be poorly documented. I wouldn't worry so much that it doesn't exactly match the schematic, but rather that the parts that ARE there are working.

Don't spend a lot of time testing the caps. They are all old. Just replace them.

73

-Jim
NU0C

On Mon, 29 Jan 2024 10:08:48 -0800
"Rick K8EZB" <frboswell@...> wrote:

Now into troubleshooting this RV75. I have the two boards out and am working on learning how the components on each board relate to the circuit diagram in my RV75 manual. I am not finding a 1:1 correspondence between the manual diagram and the components on the RF & Analog board. In particular, one of the damaged resistors does not appear to be on the circuit diagram and several small value bypass capacitors shown in the diagram I am unable to find on the board. In tracing the circuits involved with the burned resistors it is apparent that both of these are in the 13v circuits switched by S1.? ?My manual is dated December 1982 and the board in question has the designation " 6020D? 1982" etched into the copper at the edge of the board. I am wondering why my board and manual disagree; apparently the board or manual were changed over time. .Any guidance on this?

I have done a quick and dirty in-circuit check of the electrolytics on both boards and am seeing values within about 10 per cent with the exception of two caps on the digital board which show around 1000 mfd when the caps are spec'd at 22 mfd; I havent yet traced this circuit to see if there is a reason elsewhere why this reading is not closer to the listed cap values but I suspect the tester is seeing another connected capacitor elsewhere in the circuit. I'll get to this soon.

Thanks for any guidance.

Best,
Rick
K8EZB

--

73

-Jim
NU0C

Joe,

The PS7 has a spot on the rear panel for mounting a Drake FA7 or equivalent cooling fan. Look for the square plate right behind the main filter caps. There is a two pin AC socket next to is to power a 120VAC fan. And you do want to pull air out.

73

-Jim
NU0C

On Mon, 29 Jan 2024 10:14:30 -0800
"Joseph K4JNG" <jgraif1@...> wrote:

I hope it's OK to combine these two questions into a single thread. First, now that I have acquired a PS7, I thought about using my PS75 to power my CW75 and SP75, but with no rig attached to it, how would I power it up? Second, I have a 4.5" X 4.5" box fan that I wish to use on the PS7. Looking at the top from the front (strap) side, which "quadrant" would be the best over which to situate the fan. Aslo, I assume the fan should be "sucking" air out as opposed to blowing it in.

Thanks for your time and attention.

73,
joe
K4JNG

--

73

-Jim
NU0C

I hope it's OK to combine these two questions into a single thread. First, now that I have acquired a PS7, I thought about using my PS75 to power my CW75 and SP75, but with no rig attached to it, how would I power it up? Second, I have a 4.5" X 4.5" box fan that I wish to use on the PS7. Looking at the top from the front (strap) side, which "quadrant" would be the best over which to situate the fan. Also, I assume the fan should be "sucking" air out as opposed to blowing it in.

Thanks for your time and attention.

73,
joe
K4JNG

Now into troubleshooting this RV75. I have the two boards out and am working on learning how the components on each board relate to the circuit diagram in my RV75 manual. I am not finding a 1:1 correspondence between the manual diagram and the components on the RF & Analog board. In particular, one of the damaged resistors does not appear to be on the circuit diagram and several small value bypass capacitors shown in the diagram I am unable to find on the board. In tracing the circuits involved with the burned resistors it is apparent that both of these are in the 13v circuits switched by S1.? ?My manual is dated December 1982 and the board in question has the designation " 6020D? 1982" etched into the copper at the edge of the board. I am wondering why my board and manual disagree; apparently the board or manual were changed over time. .Any guidance on this?

I have done a quick and dirty in-circuit check of the electrolytics on both boards and am seeing values within about 10 per cent with the exception of two caps on the digital board which show around 1000 mfd when the caps are spec'd at 22 mfd; I havent yet traced this circuit to see if there is a reason elsewhere why this reading is not closer to the listed cap values but I suspect the tester is seeing another connected capacitor elsewhere in the circuit. I'll get to this soon.

Thanks for any guidance.

Best,
Rick
K8EZB

Glad to hear. Enjoy the newly calibrated meter.

73? Bob

开云体育

Let me see what I have in the collection.

Everyone!

开云体育

CR12 and R22 on the Parent board. See attached image.

73

-Jim
NU0C

On Mon, 29 Jan 2024 01:57:05 +0000
"Art Delibert" <radio75a3@...> wrote:

I'm hoping someone with access to a TR-7 schematic can answer this question. In the service manual for the R-7 receiver, it says, with respect to the PTO buffer board, "When +10V (RCT) is applied to module pin 22, CR301 turns on through an identical diode and load resistor located in the TR7, thus coupling the R7 PTO to the TR7 synthesizer."

Can someone please let me know the size of that load resistor in the TR7?

Thanks in advance.

Art Delibert, KB3FJO

--

73

-Jim
NU0C

Recently, I sent my Drake R4A and T4X to WB4HFN for a restoration and repair. ?He was able to restore my R4A, but the T4X was deemed unrepairable due to the broken band switch, intermittent function switch and bad final tubes, ?I am now searching for a working Drake T4X at a reasonable price. ?I have a working power supply, so I only need the transmitter itself. ?If anyone has a working Drake T4X that they would be willing to sell, please contact me. ?Thank you for reading this. ?73, Kevin W2TVS

开云体育

Decided to do something constructive today, so I replaced the vernier
drive on my L-4B.? The original vernier has very little resistance when
I turn it.? Here's some before and after pics.? The ever so slightly
longer, maybe 1/2" or so leads on the neon lamps I replaced were long
enough I could rotate the front panel out of the way.? I may disassemble
the original vernier and look at repairing it.? Pretty much a beginner
when it comes to machinist work, but I do have a mini lathe.? Upgrading
it to a 16" bed is another on the round to it projects list.? Thanks
again for all the comments on the vernier drive.

73

Stan
KM4HQE

Hey Steve,

Thanks for the info. I do have a spare TR-4 that I can try. It needs a tiny bit of work and it’ll be ok to do some testing on. ?

It’s a new problem for sure. When I first got the set, the dial tracking and the gears on the RV-4 were way off, so once that was all lined back up and put in to place the thing worked like it should. Hasn’t been tinkered with much and neither has the TR-4. ?

I will try to look at it today and see what I can isolate. Thanks again!

Cody N4AAT

Per W8JI, Vaseline liquifies at just 100 Deg F...and makes for excellent fire starter.?

?

Paul's method of synthetic grease? is top notch.? It will LAST.?