TRIO TS-510 QRP Mod

[hiro, JJ1FXF]

Hi, all.

My name is hiro and just joined this forum. I’m a TRIO TS-510 user and looking forward some mod info of its QRP.

TS-510 outputs about 150W with two S2001s. And I’d like to ease the PA tubes to last for long.

My idea is adding a 1.2k ohm registor just after the SG switch limit the SG current.

Is there anyone who tries this or another way to reduce its PA output?

Any info or just pointers are very much appreciated.

Thanks in advance.

// hiro, JJ1FXF

[Radio Wrangler]

I think that if you want QRP, you could remove both PA valves and just use the driver into the pi network. What does it use 12BY7A?

David GM4ZNX

[hiro, JJ1FXF]

Thanks for your reply, David.

What I mean by QRP is not much that. I’d like to output about half power, maybe 60-80W with two PA valves.

// hiro, JJ1FXF

[Martin G7MRV]

Can you not simply reduce the level of the drive input to the PA?

If you havent already got it, you can find the service manual here http://www.wb4hfn.com/KENWOOD/Manual...e%20Manual.pdf

[Radio Wrangler]

You should be able to achieve what you want by setting the pi-tank for less loading. Still tuned to resonance and still with normal drive to the PA. You should get a normal tuning dip in anode current, but to lower anode current. No modifications needed, just a change in tuning procedure.

David

[hiro, JJ1FXF]

Martin, David,

Many thanks for your replies.

If tuning the DRIVE down, I’m afraid that receiving signals get weak.

If tuning the LOAD down, doesnt the PI-Network mismatch that may cause to damage the PA tubes?

// hiro, JJ1FXF

[Radio Wrangler]

It's not a radio I'm familiar with, but I suspect the drive control may be the tuning for the resonant coupler between the driver stage and the PA. It was common practice in Japanese transceivers of this era to gang this tuning control with the receiver preselector. In early Yaesu rigs the lack of trimmers meant that you had to get a genuine Toshiba 12BY7A valve or else you were stuck with the transmitter and the receiver peaking at different positions on the drive/preselect control and you had to shift the knob every over.

Light loading from the Pi tank, and running at lopwe PA anode current will not damage PA valves, it is being kind to them and you ought to get more life from them.

There is ALWAYS a mismatch between the PA anode and the antenna, the pi tank is to rationalise this. There is a false belief that PA and antenna must be matched, but it is false. The pi tank transforms the impedance of the antenna into a higher impedance which it presents to the power amplifier valves. They are happy to drive a lighter load.

For more information on this, look up 'load lines' in any good text book.

Matching is a very special circumstance which is only used in limited conditions, most often we are loading a source, not matching it. Matching something tries to take the mathematically calculated maximum power from a source, irrespeective of whether that amount will destroy the source! Loading on the other hand takes a planned amount of power. Think of your pi tank as a gearbox. If you drove your car everywhere in a gear that put the engine at max power revs, you would get wonderful acceleration, but your engine would not last long. More sensible to drive in a gear that extracts only the needed amount of power and keeps the engine more within its comfortable speed range.

David

[hiro, JJ1FXF]

David,

Your detailed explanation is very much appreciated. Thanks a lot!

There are three knobs on TS-510, DRIVE, PLATE and LOAD, which are PRESELECT, PLATE and LOADING on YAESE rigs.

The DRIVE knob controls two VCs (Variable Capacitor) at once, one VC for preserecting signal reception and the other for matching btw driver tube (yeah, 12BY7A on TS-510) and final tube (S2001).

And PLATE knob controls PA side VC before a coil of PI tank and LOAD knob controls ANT side of VC after the coil.

Usually I operate both LOAD and PLATE knobs to maximize the RF output.

Do you mean to say that both knobs can be tuned for the RF output as I want such as 50W? Or only the LOAD or PLATE should be tuned to lessen the RF output but the other knob is still tuned to maximize the RF output?

This is really exciting to know because I can set up the PA output as I want, that is very useful especially when I QSO with super local stations. I can use this technique on my other legacy rigs such as TS-520.

Again, thanks for your info.

// hiro, JJ1FXF

[Radio Wrangler]

Yes, "Drive" is adjusted for max output

"Plate" should also be adjusted for max output == a dip in the anode current

and "Load" should be adjusted to get the anode current/ output power you want.

So peak up the Drive control, adjust plate to dip the anode current. the usual tuning process is then to check whether the anode current is at the target value or not. If it isn't then adjust "Load" a little and re-adjust "Plate" because the position of the dip will have moved... then you check to see if the anode current is now right. You keep on offsetting "Load" and re-dipping "Plate" until you arrive at the intended anode current.

Your transceiver should now be producing its full output power.


For lower output power, the above process is also used, but the target value of the anode current is reduced. Aim for about half the current given in the tune-up procedure in the manual, and you should get about half the normal power.

Your anode dissipation in your PA valves is reduced, so stresses are reduced. THe anode voltages don't swing as low so screen grid dissipation is reduced, too. And at the lower current, the cathodes are not having to emit as many electrons. The valves are having a nice time!

There is a limit to how much you can reduce power this way, so if you wanted to get down to 5 Watts for a QRP-club competition, then you'll have difficulty. This was what I first thought you were wanting, when I suggested using the driver without the PA.

David

[hiro, JJ1FXF]

David,

Many, many thanks for your specific guidelines. Now I can give my PA tubes a peace.

I am a kind of come-back HAM after 40yrs of QRT. And this time, I am so much interested in tubes and so have got a TRIO TS-510 which contains 14 tubes in it.

The rig was muddy and broken in several units and parts, but now it’s working.

It’s not actually working at 100%, VFO still drifts a lot, 15m and 10m Xtal seem not to oscillate and some other stuff I’m still working on.

However, it is really exciting to know more about the rig and tubes.

Again, many thanks for your kind replies.

Looking forward to QSO some day!

73,

// hiro, JJ1FXF

[Radio Wrangler]

A couple of sunspot peaks ago, I worked a station in Japan with about 2Watts of CW from a little transistor transmitter I built on a small scrap of raw PCB material, an Eddystone EA12 receiver and a dipole over the top of my house. It felt like real amateur radio!

Have fun,
David

[hiro, JJ1FXF]

40yrs ago, when I was a newbie HAM, DX stations were everywhere on 15m. But when I come back here after long QRT, I do not hear even JA on the same band.

I am looking forward to another high sunspot season coming back and so started resorting my 40yr old rig alive, which is TRIO TS-520X.

He is working fine now. And now I wanna know more about the root of TS-520, that is TS-510, I think.

Restoring is fun!, very much. Tubes teach me a lot what I forgot and didn’t know.

// hiro, JJ1FXF

[Gi4CZW Cliff]

I find this interesting as I have a sked with a 'ham, who says he reduces his transmitter output, by switching in an extra resistor, to reduce his 6146 screen grid voltage. The valve characteristic charts that I see, don't show that variation. Is it an option ? Cliff.

[hiro, JJ1FXF]

When I compared the final boxes of my TS-520X (10W model in Japan) and TS-520D (100W model), I found the 1.2k ohm registor of TS-520X in the line from SG switch to screen grid of S2001.

I jumped the 1.2k ohm registor of TS-510X and then it output 40W. Then when I
switched 400V to 800V from the transformer to the plate of S2001, then it output 60W.

So this might work at TS-510 too, I thought.

BTW, the 1.2k ohm registor isn’t described in its schematic.

[Gi4CZW Cliff]

Hello Hiro, I spoke with my contact today, on ssb full power, he has anode volts of 800V on his pair of 6146B's and 180mA of anode current with "AHHHHH..." into microphone. With the extra screen grid resistor, the HT is the same but anode current down to 120mA's. He tells me this will enhance valve life by easing pressure on the cathode coating. I was not able to find a valve characteristic chart for 6146B/S2001 of anode voltage against anode current at different values of screen grid voltage but did get one for 6L6GC. So, not sure how relevant that info is for you. Cliff.

[Radio Wrangler]

The reduced screen voltage is a way to get substantially better valve life with a relatively small reduction in power. Notice how valves intended for continuous operation on broadcast transmitters tend towards low current density at their cathodes and get their power from very high anode voltages.

Hiro's wanting a substantial power reduction so as not to hog a frequency over an unnecessarily large geographic area. A most laudable aim!

Tuning the pi-tank for light loading will also reduce the cathode currents in any class-AB or class-C transmitter PA. It gives you variable power without internal modifications. Also, the pi-tank is running with a higher Q factor giving better harmonic suppression.

David

[hiro, JJ1FXF]

Cliff, David,

Thanks for your replies.

The reason why I want to QRP is because the balan of DP is my hand-made and so maybe 50w++ is the maximum for it.

I will add extra registor soon later but meantime just controlling the LOAD is just enough for the test anyway.

My 510 is working well now. The separation of signals isn’t good as latest rigs but the sound of signal reception is warm and comfortable to my ears.

[G4YVM David]

Normally one feeds a voltage into the ALC socket at the rear to drop the output. Just dropping the drive isnt good for them on ssb

[G4YVM David]

This from another thread elsewhere.

I am.not the author.



I'm just building a rig from scratch using a pair of 6146's in the final and have been studying the data sheets, various designs and operational notes from the manufacturer.

Using a 6146 at reduced power output will increase its life PROVIDING the anode load impedance is not too high which would result in excessive voltage on speech peaks and thus potentially flash over.

As others have mentioned - load it up for say 75% maximum power output then reduce drive via ALC or some other means down to the desired output power.

I suspect this idea that running a 6146 at low output shortens its life came about by operators tuning the Pi tank for low output power resulting in an anode load impedance which was too high and out of spec for the valve - most likely resulting in excessive screen current which would quickly destroy the valve.

Best way is tune for full output then using a simple circuit of 9v battery and a variable resistor tap into the ALC circuit and reduce power that way.

[hiro, JJ1FXF]

Thanks, David.

So it means, just LOAD down may possibly cause to damage the final tube.

What is the simple circuit of 9V battery and the VR? Do you have any pointer?