David,

I am not positive but I think there were two (or more) versions of the AC-3.? I think mine was the really early one,

with choke input filter for better regulation at the drawback of extra cost.? The later AC-3 is pretty much like the AC-4.

I think this is the one that you have.? That's why it refers to the MS-3 and RV-3.? The AC-4 did have an aluminum cover,

that might be the reason they changed the designation.? The paper covered caps in yours could lose their covers and

then would have 400v exposed, why I think Drake added the cover.

I'd try to find the schematic that matches what you have, then order caps, etc. to match.

?

73,

Gary

WB6OGD

Don't waste money on those pcb rebuild kits.

?

I was able to put new (and cheaper) radial caps under the chassis.? New caps are waaayy smaller!

?

See the photos of an AC-3 I rebuilt a few years ago.? The new caps, diodes, etc. fit the existing

terminal strips like they were made for them.

?

And someday in the distant(?) future it will be easier to replace the caps than it would be if they were

on a pcb.

?

The AC-3 has a big resistor.? It got too hot under the chassis so I mounted it on top and made an

aluminum heatsink/safety shield over it.

?

Even though this was an early Drake supply, I paired it with a TR-4C and it worked great.? The AC-3

is actually a better supply with its big choke.

?

73,

Gary

WB6OGD

?

Talk about tunnel-vision!

He said TR-4 and it never even occurred to me to even look closely

at the faceplate.

We were standing in a non climate-controlled space while talking,

and it was cold.

'And that's my story, and I'm sticking to it ..."

Now, I have to learn what the difference is between the TR-4 and

the TR-4C.

Thanks!

On 1/27/25 14:43, Steve Wedge, W1ES/4 via groups.io wrote:

Exactly, which means that any kid or critter could touch dangerous voltages.

Steve Wedge, W1ES

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

Sent with secure email.

On Monday, January 27th, 2025 at 12:32 PM, VE7PS via groups.io <ve7ps@...> wrote:

And the AC-3 did not have a top cover like the AC-4.

PS

On Mon, Jan 27, 2025 at 9:28?AM Steve Wedge, W1ES/4 via <w1es=[email protected]> wrote:

The circuit board for the rebuild kit mounts on top of the chassis. You can also do a 1 for 1 replacement of the capacitors with cans, which is more expensive but preserves the original layout. If you put the new caps underneath, you can leave the originals, unconnected, on top. It is more difficult to mount caps underneath but it is certainly doable and I had done several that way. What you save on the new board, you more than make up with time spent. Everyone's equation of time vs cost is different...

Steve Wedge, W1ES

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

Sent with secure email.

On Monday, January 27th, 2025 at 12:22 PM, DavidC KD4E via <qrv=[email protected]> wrote:

I don't understand the 'cage' thing.

There a solid metal plate over the bottom of this PS.

Thanks

On 1/27/25 11:52, Evan via wrote:

As a side note, some prefer the AC-3 over the AC-4 due to the "open air" sort of cooling while the AC-4 has a small number of "hot air exhaust slots". I have no personal experience with the AC-3 so I am not aware of reliability versus the AC-4.

On Monday, January 27, 2025 at 11:47:12 AM EST, Steve Wedge, W1ES/4 via <w1es@...> wrote:

I would simply go ahead and re-cap this supply. Paper bodied electrolytic capacitors are prone to dry out.

If you want to wait, replace just the bias supply’s capacitor, as if you lose your bias supply, your finals, at best, will be stressed beyond their ratings, shortening the life of the tubes.

The rebuild kit for the AC-3 costs more than the one for the AC-4 because it needs a “cage” over the board to prevent contact with dangerous voltages. It is well worth it, though.

Steve Wedge, W1ES

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

Sent from for iOS

On Mon, Jan 27, 2025 at 10:54, DavidC KD4E via <qrv@...> wrote:

I accepted a trade offer of a TR-4 for my troublesome TR-3.

Opened things up and have a few questions for those in the know ...

Images here:

The power supply has some sort of filmy deposit on top - I'm thinking

it's residue from tobacco.

1. I'm real shy about putting moisture on the tops of the paper
electrolytics

but would WD-40 or a citrus-based cleaner using a q-tip be safest for the

chassis?

2. Do the caps appear to be original? (The rig works but I'd rather update

things, if the caps are ancient, prior to setting it up on my operating
desk.)

3. Does the serial number reveal anything useful, please?

Thanks,

David KD4E

On 2025-01-27 07:07, NU2W via groups.io wrote:

I will stick with the old way---big heavy sig gens, oscilloscope,
muti-meters....

*** Alas I cannot. Limited bench/storage space and bad back. Back in
my salad days, I put in a few years fixing and maintaining big old heavy
test equipment, so there's a bit of nostalgia about that...


There's some really neat little stuff out there now. Right here, I have
a project. It's a signal generator I bought from "AF&CH" in Ukraine on
Ebay. It's
based on an AD9910 Direct Digital Synthesis chip. It generates nice
sine waves using a 900MHz sample clock.
It can also be goosed up to 1.5gHz, but they recommend fan cooling if
you do that.

For HF frequencies, 900MHz is plenty. Spurious are 50dB down. It has a
built in
attenuator - 1 dB steps from 0dBm down to -72dBm.

It wasn't cheap; I bought it fully assembled, with an OCXO ( Oven
Compensated Crystal Oscillator ).

It's got an Arduino card bolted to it; I plan to program that to
implement a signal generator
with a big tuning knob.

- Jerry, KF6VB

Interested in replies to this as I have a TR-4C on my bench right now.??

One issue I chased was over-current on full power - full power tune up has the meter way over towards .6.? I've been stressing about it for a while and finally realized that the current meter is way off.? So, I'm not supplying adequate bias and my current draw at full power is probably OK.? I verified by measuring voltage drops across the 15ohm resistors. I also remember that when I put the TR-4C on the power supply which had previously been set up for my TR-3 the initial bias reading was right about .2 instead of .1.? I didn't think about it at the time and just reset the bias at .1 for the TR-4C.? Waiting on the proper resistor now so I can get bias set correctly.? This is now on my list of things to check first when I start the restoration on one of these.? Probably not related to your problem but (another) something to add to the health checkup.

I also have some freshly baked 10M xtals to try in mine as well.

On Monday, January 27, 2025 at 01:28:02 PM CST, Dave KD5FX via groups.io <land.dave@...> wrote:

So, finally had some time to get back on this project, winter field day kept me busy over the weekend. And thanks to all in advance for everyone's help and suggestions on this project. I did all the Xmit tune up procedures on page 5-6 including the neutralization. I'm getting about 100 watts PEP output on 80/40/20 and around 15 on 15 meters while 28.0 and 28.5 bands have zero output and on 28.1 I only have 5 watts PEP output. I wonder if these tubes are bad. Does that sound like the symptoms of a nearly dead set if tubes? I haven't pulled them out for testing but I could if needed. OR? Is there something else I've missed? BTW it's still receiving OK on ALL BANDS!?

73, Dave KD5FX

?

Don't waste money on those pcb rebuild kits.

?

I was able to put new (and cheaper) radial caps under the chassis.? New caps are waaayy smaller!

?

See the photos of an AC-3 I rebuilt a few years ago.? The new caps, diodes, etc. fit the existing

terminal strips like they were made for them.

?

And someday in the distant(?) future it will be easier to replace the caps than it would be if they were

on a pcb.

?

The AC-3 has a big resistor.? It got too hot under the chassis so I mounted it on top and made an

aluminum heatsink/safety shield over it.

?

Even though this was an early Drake supply, I paired it with a TR-4C and it worked great.? The AC-3

is actually a better supply with its big choke.

?

73,

Gary

WB6OGD

?

Exactly, which means that any kid or critter could touch dangerous voltages.

Steve Wedge, W1ES

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

Sent with secure email.

On Monday, January 27th, 2025 at 12:32 PM, VE7PS via groups.io <ve7ps@...> wrote:

And the AC-3 did not have a top cover like the AC-4.

PS

On Mon, Jan 27, 2025 at 9:28?AM Steve Wedge, W1ES/4 via <w1es=[email protected]> wrote:

The circuit board for the rebuild kit mounts on top of the chassis. You can also do a 1 for 1 replacement of the capacitors with cans, which is more expensive but preserves the original layout. If you put the new caps underneath, you can leave the originals, unconnected, on top. It is more difficult to mount caps underneath but it is certainly doable and I had done several that way. What you save on the new board, you more than make up with time spent. Everyone's equation of time vs cost is different...

Steve Wedge, W1ES

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

Sent with secure email.

On Monday, January 27th, 2025 at 12:22 PM, DavidC KD4E via <qrv=[email protected]> wrote:

I don't understand the 'cage' thing.

There a solid metal plate over the bottom of this PS.

Thanks

On 1/27/25 11:52, Evan via wrote:

As a side note, some prefer the AC-3 over the AC-4 due to the "open air" sort of cooling while the AC-4 has a small number of "hot air exhaust slots". I have no personal experience with the AC-3 so I am not aware of reliability versus the AC-4.

On Monday, January 27, 2025 at 11:47:12 AM EST, Steve Wedge, W1ES/4 via <w1es@...> wrote:

I would simply go ahead and re-cap this supply. Paper bodied electrolytic capacitors are prone to dry out.

If you want to wait, replace just the bias supply’s capacitor, as if you lose your bias supply, your finals, at best, will be stressed beyond their ratings, shortening the life of the tubes.

The rebuild kit for the AC-3 costs more than the one for the AC-4 because it needs a “cage” over the board to prevent contact with dangerous voltages. It is well worth it, though.

Steve Wedge, W1ES

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

Sent from for iOS

On Mon, Jan 27, 2025 at 10:54, DavidC KD4E via <qrv@...> wrote:

I accepted a trade offer of a TR-4 for my troublesome TR-3.

Opened things up and have a few questions for those in the know ...

Images here:

The power supply has some sort of filmy deposit on top - I'm thinking

it's residue from tobacco.

1. I'm real shy about putting moisture on the tops of the paper
electrolytics

but would WD-40 or a citrus-based cleaner using a q-tip be safest for the

chassis?

2. Do the caps appear to be original? (The rig works but I'd rather update

things, if the caps are ancient, prior to setting it up on my operating
desk.)

3. Does the serial number reveal anything useful, please?

Thanks,

David KD4E

On Jan 27, 2025, at 1:44?PM, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:

?

I believe that the Harbach set is what's sold on Nationwide.? Harbach was sold on to keep it going.

Steve Wedge, W1ES

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

Sent with secure email.

On Monday, January 27th, 2025 at 2:03 PM, Tony Sokol via groups.io <tony.sokol@...> wrote:

Perfect. That’s what I thought but I wanted to make sure. I did see KE9PQ’s rebuild kits which look really good. I was sorry to see that Harbaugh seems to be winding down since I have installed many of his over the years.?

Thanks

? Tony

On Jan 27, 2025, at 7:37?AM, David via groups.io <david.w5xu@...> wrote:

?

Yes.? There are even rebuild hardware for each type available.

David Assaf III

W5XU, VP8RXU

?

On Mon, Jan 27, 2025 at 1:14?AM Tony Sokol via <tony.sokol=[email protected]> wrote:

? ? ?I have in my collection of “stuff” two Drake AC3’s. One is a really early version and the other is a later version with a lot of iron. My question is, are all AC versions capable of driving all versions of 4-Line transmitters and transceivers??

? ? Thanks,
Tony - W9JXN

On Jan 27, 2025, at 1:44?PM, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:

?

I believe that the Harbach set is what's sold on Nationwide.? Harbach was sold on to keep it going.

Steve Wedge, W1ES

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

Sent with secure email.

On Monday, January 27th, 2025 at 2:03 PM, Tony Sokol via groups.io <tony.sokol@...> wrote:

Perfect. That’s what I thought but I wanted to make sure. I did see KE9PQ’s rebuild kits which look really good. I was sorry to see that Harbaugh seems to be winding down since I have installed many of his over the years.?

Thanks

? Tony

On Jan 27, 2025, at 7:37?AM, David via groups.io <david.w5xu@...> wrote:

?

Yes.? There are even rebuild hardware for each type available.

David Assaf III

W5XU, VP8RXU

?

On Mon, Jan 27, 2025 at 1:14?AM Tony Sokol via <tony.sokol=[email protected]> wrote:

? ? ?I have in my collection of “stuff” two Drake AC3’s. One is a really early version and the other is a later version with a lot of iron. My question is, are all AC versions capable of driving all versions of 4-Line transmitters and transceivers??

? ? Thanks,
Tony - W9JXN

I just added two pics of the back panel (images 11 & 12) - in case the
serial number

provides any useful context.

Thanks,

David KD4E

On 1/27/25 13:19, DavidC KD4E via groups.io wrote:

Looking over the TR-4 it appears generally clean, but I spotted

a loose wire (see the yellow wire looped over the switch wafer in

Image 8) here ... and

rust on the ball bearings in Image 10.

I received second-hand information that this rig was 'gone through'

by Ron, KB4HFN, several years ago - perhaps the disconnected wire

was part of a mod of some sort?

(The rig has been in non-climate controlled storage, by the Ham from

whom I received it, for about three years. It's unclear how long it may

have sat unused prior to that. It was tested on 10m prior to the swap.

He chose 10m because all of his other antennas were damaged or

destroyed by a hurricane a few months back.)

Thanks,

David KD4E

Perfect. That’s what I thought but I wanted to make sure. I did see KE9PQ’s rebuild kits which look really good. I was sorry to see that Harbaugh seems to be winding down since I have installed many of his over the years.?

Thanks

? Tony

On Jan 27, 2025, at 7:37?AM, David via groups.io <david.w5xu@...> wrote:

?

Yes.? There are even rebuild hardware for each type available.

David Assaf III

W5XU, VP8RXU

?

On Mon, Jan 27, 2025 at 1:14?AM Tony Sokol via <tony.sokol=[email protected]> wrote:

? ? ?I have in my collection of “stuff” two Drake AC3’s. One is a really early version and the other is a later version with a lot of iron. My question is, are all AC versions capable of driving all versions of 4-Line transmitters and transceivers??

? ? Thanks,
Tony - W9JXN

And the AC-3 did not have a top cover like the AC-4.

PS

On Mon, Jan 27, 2025 at 9:28?AM Steve Wedge, W1ES/4 via <w1es=[email protected]> wrote:

The circuit board for the rebuild kit mounts on top of the chassis. You can also do a 1 for 1 replacement of the capacitors with cans, which is more expensive but preserves the original layout. If you put the new caps underneath, you can leave the originals, unconnected, on top. It is more difficult to mount caps underneath but it is certainly doable and I had done several that way. What you save on the new board, you more than make up with time spent. Everyone's equation of time vs cost is different...

Steve Wedge, W1ES

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

Sent with secure email.

On Monday, January 27th, 2025 at 12:22 PM, DavidC KD4E via <qrv=[email protected]> wrote:

I don't understand the 'cage' thing.

There a solid metal plate over the bottom of this PS.

Thanks

On 1/27/25 11:52, Evan via wrote:

As a side note, some prefer the AC-3 over the AC-4 due to the "open air" sort of cooling while the AC-4 has a small number of "hot air exhaust slots". I have no personal experience with the AC-3 so I am not aware of reliability versus the AC-4.

On Monday, January 27, 2025 at 11:47:12 AM EST, Steve Wedge, W1ES/4 via <w1es@...> wrote:

I would simply go ahead and re-cap this supply. Paper bodied electrolytic capacitors are prone to dry out.

If you want to wait, replace just the bias supply’s capacitor, as if you lose your bias supply, your finals, at best, will be stressed beyond their ratings, shortening the life of the tubes.

The rebuild kit for the AC-3 costs more than the one for the AC-4 because it needs a “cage” over the board to prevent contact with dangerous voltages. It is well worth it, though.

Steve Wedge, W1ES

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

Sent from for iOS

On Mon, Jan 27, 2025 at 10:54, DavidC KD4E via <qrv@...> wrote:

I accepted a trade offer of a TR-4 for my troublesome TR-3.

Opened things up and have a few questions for those in the know ...

Images here:

The power supply has some sort of filmy deposit on top - I'm thinking

it's residue from tobacco.

1. I'm real shy about putting moisture on the tops of the paper
electrolytics

but would WD-40 or a citrus-based cleaner using a q-tip be safest for the

chassis?

2. Do the caps appear to be original? (The rig works but I'd rather update

things, if the caps are ancient, prior to setting it up on my operating
desk.)

3. Does the serial number reveal anything useful, please?

Thanks,

David KD4E