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Author Topic: Kenwood TS-570 D Fan Problem  (Read 6086 times)
WA7PZR
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Posts: 8




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« Reply #15 on: March 23, 2013, 11:12:56 PM »

That's worth a shot.
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KA5IPF
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Posts: 974


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« Reply #16 on: March 24, 2013, 10:45:06 AM »

yeah 14.000.00 showing and actually being 13.000.95. it's not a lot, but it is annoying. with that fan sucking the heat out it stays right on freq. with summer coming and it being used for fsk it should be closer than that.


The answer to the non-problem is contained in the above quote; "it being used for fsk". FSK is a 100% duty cycle mode and generates a lot of heat. The stock 570 uses a reference xtal that is not insulated from chassis temperature changes(final and PLL mounted to same aluminum chassis) and will change as the temperature changes. The 50Hz drift is well within the spec of the stock radio. Per owners manual less than +/-10PPM from -10 to 50 deg C. That's +/- 140 Hz on 20M. Since the "normal" Kenwood temperature circuit turns on the fan at 40deg C (105 F) I would guess the xtal would move. Actually that's a small amount of drift under those circumstances.

If greater stability is desired/required then you can Band-aid (FAN) or fix (TCXO), your choice. Realize the fan fix will only work up to a certain temperature (summers coming). I wouldn't change the internal fan circuit.

Since the SO-2 TCXO option is hard to find go to Product Reviews and search for "N3BA VCTCXO Module" It may solve the problem.

Clif
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W8JX
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« Reply #17 on: March 24, 2013, 04:24:57 PM »

The answer to the non-problem is contained in the above quote; "it being used for fsk". FSK is a 100% duty cycle mode and generates a lot of heat. The stock 570 uses a reference xtal that is not insulated from chassis temperature changes(final and PLL mounted to same aluminum chassis) and will change as the temperature changes. The 50Hz drift is well within the spec of the stock radio. Per owners manual less than +/-10PPM from -10 to 50 deg C. That's +/- 140 Hz on 20M. Since the "normal" Kenwood temperature circuit turns on the fan at 40deg C (105 F) I would guess the xtal would move. Actually that's a small amount of drift under those circumstances.

Have you ever owned and used a 570?  It is a very stable rig. Stability specs are worst case scenario and from a temperature range of -10c to +50c which is not normal shack operation. In using one for nearly 13 years I have never detected any discernible drift in its use even over a period of several hours on same frequency. Rather that hunting for gremlins in the VFO reference oscillator, one need to find problem with cooling fan circuit. Mine never gets more than just warm to touch in digital before fan comes on. I see no need for TCXO in a 570 except maybe a S model for 6 meters.
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KA5IPF
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« Reply #18 on: March 24, 2013, 06:17:37 PM »

The answer to the non-problem is contained in the above quote; "it being used for fsk". FSK is a 100% duty cycle mode and generates a lot of heat. The stock 570 uses a reference xtal that is not insulated from chassis temperature changes(final and PLL mounted to same aluminum chassis) and will change as the temperature changes. The 50Hz drift is well within the spec of the stock radio. Per owners manual less than +/-10PPM from -10 to 50 deg C. That's +/- 140 Hz on 20M. Since the "normal" Kenwood temperature circuit turns on the fan at 40deg C (105 F) I would guess the xtal would move. Actually that's a small amount of drift under those circumstances.

Have you ever owned and used a 570?  It is a very stable rig. Stability specs are worst case scenario and from a temperature range of -10c to +50c which is not normal shack operation. In using one for nearly 13 years I have never detected any discernible drift in its use even over a period of several hours on same frequency. Rather that hunting for gremlins in the VFO reference oscillator, one need to find problem with cooling fan circuit. Mine never gets more than just warm to touch in digital before fan comes on. I see no need for TCXO in a 570 except maybe a S model for 6 meters.

I've owned several and worked on more that you have probably ever seen...

Clif
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W8JX
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Posts: 5366




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« Reply #19 on: March 24, 2013, 07:00:10 PM »

The answer to the non-problem is contained in the above quote; "it being used for fsk". FSK is a 100% duty cycle mode and generates a lot of heat. The stock 570 uses a reference xtal that is not insulated from chassis temperature changes(final and PLL mounted to same aluminum chassis) and will change as the temperature changes. The 50Hz drift is well within the spec of the stock radio. Per owners manual less than +/-10PPM from -10 to 50 deg C. That's +/- 140 Hz on 20M. Since the "normal" Kenwood temperature circuit turns on the fan at 40deg C (105 F) I would guess the xtal would move. Actually that's a small amount of drift under those circumstances.

Have you ever owned and used a 570?  It is a very stable rig. Stability specs are worst case scenario and from a temperature range of -10c to +50c which is not normal shack operation. In using one for nearly 13 years I have never detected any discernible drift in its use even over a period of several hours on same frequency. Rather that hunting for gremlins in the VFO reference oscillator, one need to find problem with cooling fan circuit. Mine never gets more than just warm to touch in digital before fan comes on. I see no need for TCXO in a 570 except maybe a S model for 6 meters.

I've owned several and worked on more that you have probably ever seen...

Clif

Maybe but I have found them to be very stable.  Even the 140's I have owned have been quite stable. Once I left one out in car when it got to 35 below on night. Next morning I turned it on and the display did not work and no receive (likely due to lack of PLL lock up). I left it on and covered it up with a towel and 15 minutes later it was up and running. I do not recall it really drifting but VFO knob was stiff for a while.
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ZS5WC
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« Reply #20 on: March 25, 2013, 07:51:09 AM »

I had the same problem with my TS-590s, it was getting blisteringly hot with no fan running.
I solved the issue by parallelling a 12k resistor across the thermistor terminals and the fan comes in sooner, and stays in for longer.
No more issues!..
The same could be tried with the TS-570s I guess.
I did the same with my TS-430s--a rig known for heat related issues in the PA.

73 de William
ZS4L / ZS5WC
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KA5IPF
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« Reply #21 on: March 25, 2013, 08:13:13 AM »

You're confusing not drifting with the display not changing frequency. All of the newer radios depend on the processor to display the frequency. The indicated frequency is whatever the processor tells it to be, not what it actually is. What the actual operating frequency is and the displayed frequency can vary and does. Most hams don't notice it as the quality of the crystals today and the design of the radios are much better which limits the amount of drift.

If you have a frequency counter that is accurate and stable do an experiment. Set up for the counter to measure the TX frequency on 29MHz CW mode into a dummy load. You will need a pick-off for the counter. Leave the counter on for several hours for it to stabilize. Turn on the radio and immediately transmit and measure the frequency. Do it again 1 minute later and then 5 minutes later. Write them all down. Wait for 15 and then 30 minutes and measure again. After 30 min usually they have reached operating temperature. You will probably find the change in frequency to be on the order of 100 Hz. But the display never changed. Then check it again on the hour and for several subsequent hours, you will find each reading to be slightly different. After the 30 min warm-up you have the frequency accuracy, the other measurements measure the frequency stability.

Same thing can be done by tracking WWV from cold turn-on up to the 30 minute mark. Only in tracking WWV you move the vfo knob to maintain the same tone out and note the change in indicated frequency on the radio.

There are 2 parts to accurate frequency measurement. The first is how accurate is the indicated frequency? The second is how stable is it?

In SSB operation a change of frequency is usually not noticed but on FSK or PSK31 it is.

Clif
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W8JX
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« Reply #22 on: March 25, 2013, 08:31:50 AM »

In SSB operation a change of frequency is usually not noticed but on FSK or PSK31 it is.

It depends how good your ear is. I can easily tell when a SSB station has drifted off zero beat using headphones.
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