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Old 23rd May 2024, 5:24 pm   #1
Damo666
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Default Kenwood TS-530S plate current (Ip) query

Hello all,

I'm used to "plug 'n play" Transistorised rigs, & this is the first Kenwood hybrid tube rig I've owned.

I'm familiar with all the functions, as they're quite elementary in comparison to modern equipment, however, I'm confused about the following.

When following the tune up procedure here with everything at its peak, I end up reaching a plate current of circa 260 - 270ma and around 120W output power on CW - https://www.k4eaa.com/tune-up.htm

I've done a bit of reading around, and the consensus is that plate current at tune up shouldn't exceed 225mA.

My questions are; how can I reduce plate current at final tune up, and will the 260 - 270mA plate current I witnessed at full tune up have damaged the tubes?

For what it's worth, when tuning at full power, I never keyed for more than about 2 or 3 seconds, let the tubes rest for 30 seconds between steps, so was well within the maximum of 10 seconds key up period at full power.
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Old 23rd May 2024, 5:59 pm   #2
Cruisin Marine
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Default Re: Kenwood TS-530S plate current (Ip) query

I think your valves/tubes should be OK.
You need to make sure the bias is correct according to the manual, and remember when you tune up, the anode load is set for MINIMUM current, and loading is associated with that.
The whole procedure should be either in the manual or on the net somewhere for you to find. I don't know that rig personally, sorry.
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Old 23rd May 2024, 8:16 pm   #3
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Default Re: Kenwood TS-530S plate current (Ip) query

Hello,

Many thanks for the reply.

I'm glad the tubes will probably be OK.

I'm not sure what you mean when you mention "Anode load", but I start with the following positions at tune up:- drive control centred, plate cursor at band of use, and load fully counter clockwise (fully meshed).

I've found that bias for SSB should be 60mA, and that's correct.

I'm just trying to establish the correct procedure to reduce plate current to 225mA at final tune up, as opposed to the ~265mA I'm seeing, as I'm not happy with this & most mention that 225mA should be the limit.

I'm not sure how ubiquitous tubes are for these now as they're a 80s rig if I'm not mistaken.
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Old 23rd May 2024, 8:39 pm   #4
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Default Re: Kenwood TS-530S plate current (Ip) query

Anode load (I ment anode tune) = plate tuning (I got it wrong firstly, typing too fast, I should have said that to avoid confusion). Have you adjusted the drive level and set the CAR control?
Those instructions you linked to look good to me.
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Old 23rd May 2024, 8:57 pm   #5
G6Tanuki
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Default Re: Kenwood TS-530S plate current (Ip) query

Are you doing the tune and load thing with a proper 50 Ohm non inductive RF load connected, or are you coupling the radio to a real world antenna (which may display some odd reactance??).

I always recommend doing the tune and load thing into a proper dummy load so you get the right points for the tune and load, only then do you connect a real world antenna (through an antenna matcher if necessary) and you then don't touch the transmitter tune/load but do all the subsequent adjustments on the matcher.
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Old 23rd May 2024, 10:02 pm   #6
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Default Re: Kenwood TS-530S plate current (Ip) query

QST December 1979 had an article "Tune up swiftly, silently and safely". Unfortunately can't find it online, but I have my own home copied pdf of my magazine copy on one of my pc. I built two in total of these, each in a diecast box.
It is a unit between the tx and atu, that has a switch to send tx to a dummy load or the atu.
In use, you select the dummy load, so tx sees the correct 50R load. In this position is a small ferrite ring transformer in series, feeding a diode and resistor bridge. One arm is a small 50R resistor, the other is the atu.
Once the bridge is balanced, with a small uA dc meter, you then switch the tx through to the atu and all should then be tuned properly.
I think I have the description correct?
The beauty is you tune your pa power into a dummy load whilst adjusting the atu with a few, maybe tens of milliwatts of rf.
Saves qrm and saves stress on your pa.
Rob
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Old 24th May 2024, 8:49 am   #7
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Default Re: Kenwood TS-530S plate current (Ip) query

Quote:
Originally Posted by G6Tanuki View Post
Are you doing the tune and load thing with a proper 50 Ohm non inductive RF load connected, or are you coupling the radio to a real world antenna (which may display some odd reactance??).

I always recommend doing the tune and load thing into a proper dummy load so you get the right points for the tune and load, only then do you connect a real world antenna (through an antenna matcher if necessary) and you then don't touch the transmitter tune/load but do all the subsequent adjustments on the matcher.
Hello,

Yes, I'm tuning into a dummy load that's good upto UHF.
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Old 24th May 2024, 10:52 am   #8
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Default Re: Kenwood TS-530S plate current (Ip) query

The meter indicates 'Plate Current' by measuring the voltage across a low-value resistance in the cathode lead. Thus, 'Plate Current' is actually the sum of Ia + Ig2. It is worth checking the resistance from cathode to ground. Resistors drift high over time, which will give an erroneously high current reading. I had this problem with my TS830S and replacing the cathode resistors brought the indicated current down to an acceptable level.

Peter G3PIJ
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Old 24th May 2024, 12:22 pm   #9
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Default Re: Kenwood TS-530S plate current (Ip) query

The Pi -circuit output tuning arrangement in most valved transmitters isn't tied to 50 Ohms. It can perform the necessary impedance transformation to efficiently couple with a moderate range of antenna impedances.

It's perfectly reasonable to connect an antenna directly and to tune up the output stage to suit it. Swing the "Tune" capacitor and look for the dip in anode current. Is the current in the dip OK? You don't want to exceed the value Trio/Kenwood state because that would risk damage. Also you don't want it to be too much less if you want the power the transmitter is capable of. If you want low power you can run lower current.

So if the current in the dip isn't what you want, turn the "Load" capacitor knob a little. Do the dip thing again. Is the current better or worse? If better, try a little more in the same direction. If worse you need to try the other direction.

With small movements of "Load" with re-dipping "Tune" each time you can get yourself to a peaked condition and the right amount of anode current.

You also need to have peaked the position of the receiver preselector tuning knob because this also peaks the driver power into the transmitter output valve. Do this whenever you change frequency, but you don't need to touch it when tuning "Tune" and "Load" This adjustment SHOULD be OK by peaking the preselector on receive and you don't need to mess with it for transmitting BUT the circuit was designed around the stray capacitances of a Toshiba-made driver valve. Other makes are available as they say, but their stray C is different so you need that knob in two different positions for optimum receive and for optimum transmit! There isn't an adjustment fitted to correct for this.

So, this will get you going with an antenna and no ATU.

But you'll find that at some frequencies, you just can't get the Pi-network to do a good job. NOW you need an ATU. To use an ATU, you first tune your transmitter into a 50 ohm dummy load. Same procedure as above. And now you need to tune the ATU so that it makes the antenna look like 50 Ohms to the transmitter and all will be well.

To do this, you need something along the cable between the transmitter and the ATU. Most people will say you need a VSWR meter, which will do the job.

VSWR meters involve a bit of playing around and setting a calibration knob and switching to-and fro. This is more nuisance piled on top of what's already been a tedious job.

Some years ago I published a design for a homebrew "Dual directional wattmeter" (It's in the G-QRP Club's magazine "Sprat" issue number 61.) No switches, no cal knobs, just two meters marked in watts. One reads the power going to the antenna via the ATU, the other reads the power reflected back via the reverse route.

You adjust the ATU to minimise the reverse power. You can see the forwards power while you do it. There are many versions of this general idea, but you buy two meters only once, but with a single meter VXWR meter you condemn yourself to repeatedly switching the thing to and fro.

There you have it. How to tune your rig into anything it can handle directly. How to tune it to 50 Ohms using a dummy load, then how to tune an ATU to convert your antenna into the 50 ohms the rig is now expecting.

DAvid GM4ZNX
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Old 24th May 2024, 3:22 pm   #10
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Default Re: Kenwood TS-530S plate current (Ip) query

Quote:
Originally Posted by G3PIJpeter View Post
The meter indicates 'Plate Current' by measuring the voltage across a low-value resistance in the cathode lead. Thus, 'Plate Current' is actually the sum of Ia + Ig2. It is worth checking the resistance from cathode to ground. Resistors drift high over time, which will give an erroneously high current reading. I had this problem with my TS830S and replacing the cathode resistors brought the indicated current down to an acceptable level.

Peter G3PIJ
Hello Peter,

Thank you for this useful information.

I have a decent DMM here, so will check the resistance from the Cathodes of the finals to ground when I return home either tonight or tomorrow.

I would like to give these Cathode resistors a visual inspection, too, so do you know where they are located on the TS-530S, please?
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Old 24th May 2024, 3:26 pm   #11
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Default Re: Kenwood TS-530S plate current (Ip) query

Quote:
Originally Posted by Radio Wrangler View Post
The Pi -circuit output tuning arrangement in most valved transmitters isn't tied to 50 Ohms. It can perform the necessary impedance transformation to efficiently couple with a moderate range of antenna impedances.

It's perfectly reasonable to connect an antenna directly and to tune up the output stage to suit it. Swing the "Tune" capacitor and look for the dip in anode current. Is the current in the dip OK? You don't want to exceed the value Trio/Kenwood state because that would risk damage. Also you don't want it to be too much less if you want the power the transmitter is capable of. If you want low power you can run lower current.

So if the current in the dip isn't what you want, turn the "Load" capacitor knob a little. Do the dip thing again. Is the current better or worse? If better, try a little more in the same direction. If worse you need to try the other direction.

With small movements of "Load" with re-dipping "Tune" each time you can get yourself to a peaked condition and the right amount of anode current.

You also need to have peaked the position of the receiver preselector tuning knob because this also peaks the driver power into the transmitter output valve. Do this whenever you change frequency, but you don't need to touch it when tuning "Tune" and "Load" This adjustment SHOULD be OK by peaking the preselector on receive and you don't need to mess with it for transmitting BUT the circuit was designed around the stray capacitances of a Toshiba-made driver valve. Other makes are available as they say, but their stray C is different so you need that knob in two different positions for optimum receive and for optimum transmit! There isn't an adjustment fitted to correct for this.

So, this will get you going with an antenna and no ATU.

But you'll find that at some frequencies, you just can't get the Pi-network to do a good job. NOW you need an ATU. To use an ATU, you first tune your transmitter into a 50 ohm dummy load. Same procedure as above. And now you need to tune the ATU so that it makes the antenna look like 50 Ohms to the transmitter and all will be well.

To do this, you need something along the cable between the transmitter and the ATU. Most people will say you need a VSWR meter, which will do the job.

VSWR meters involve a bit of playing around and setting a calibration knob and switching to-and fro. This is more nuisance piled on top of what's already been a tedious job.

Some years ago I published a design for a homebrew "Dual directional wattmeter" (It's in the G-QRP Club's magazine "Sprat" issue number 61.) No switches, no cal knobs, just two meters marked in watts. One reads the power going to the antenna via the ATU, the other reads the power reflected back via the reverse route.

You adjust the ATU to minimise the reverse power. You can see the forwards power while you do it. There are many versions of this general idea, but you buy two meters only once, but with a single meter VXWR meter you condemn yourself to repeatedly switching the thing to and fro.

There you have it. How to tune your rig into anything it can handle directly. How to tune it to 50 Ohms using a dummy load, then how to tune an ATU to convert your antenna into the 50 ohms the rig is now expecting.

DAvid GM4ZNX

Hello David,

Another good bit of useful information here, so thank you also.

I will use this method.

After further reading around, I've also established that at the end of tune up, if Ip (plate current) is a tad high - the carrier control can also be used to reduce it to the 225mA that's widely suggested.

Using the carrier control to reduce IP when everything is peaked, I can go from 120W output power at 265mA to around 95W at 220mA plate current.

Last edited by Damo666; 24th May 2024 at 3:32 pm.
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Old 24th May 2024, 3:55 pm   #12
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Default Re: Kenwood TS-530S plate current (Ip) query

Quote:
Originally Posted by Damo666 View Post
I would like to give these Cathode resistors a visual inspection, too, so do you know where they are located on the TS-530S, please?
There are four 20-ohm resistors connected in parallel from cathode to ground - R2, R3, R4 and R5. Total resistance = 5 ohms. The positions are shown in the thumbnail below, copied from the Service Manual, which can be downloaded from https://www.manualslib.com/download/...d-Ts-530s.html

Peter
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Old 24th May 2024, 4:13 pm   #13
Damo666
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Default Re: Kenwood TS-530S plate current (Ip) query

Thank you, Peter, this is incredibly helpful.

As soon as I get to the rig, I will inspect these Resistors & measure the resistance then return here with my findings.

In fact, as they're now getting on a bit - I'll probably just purchase some 1% tolerance alternatives & replace them all.
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Old 24th May 2024, 5:25 pm   #14
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Default Re: Kenwood TS-530S plate current (Ip) query

Quote:
Originally Posted by Damo666 View Post
I'll probably just purchase some 1% tolerance alternatives & replace them all.
In the event of flashover or other such 6146-critical overload, these resistors can act like fuses. Make sure to fit low-wattage replacements like the originals
Peter
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Old 25th May 2024, 1:27 am   #15
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Default Re: Kenwood TS-530S plate current (Ip) query

I got around to inspecting inside the TS-530S, and all looks good - apart from a few dry joints around the tube bases.

My DMM ohmeter shows 0.7R with the probes shorted together, and, when checking the Cathode resistors, my meter indicated 5.8R, so, 5.1R which is very acceptable.

There are also a couple of decent filters in this, and nothing looks charred or abused.

Please see the attached images.
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Old 25th May 2024, 9:59 pm   #16
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Default Re: Kenwood TS-530S plate current (Ip) query

A lovely rig- glad you are the keeper, look after it well
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Old 26th May 2024, 10:05 pm   #17
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Default Re: Kenwood TS-530S plate current (Ip) query

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A lovely rig- glad you are the keeper, look after it well
They are indeed, & I certainly will.

I have a bit of modern gear that blows the TS-530 out of the water in terms of filtering & digital noise reduction, however, the build quality of this Kenwood is on another level in comparison to the modern stuff.

The internals really are a work of art & very well thought out.

I've now noticed a finicky bandswitch, so cleaning the wafers with some IPA or Servisol switch cleaner should see things improve.
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