Discussion:
PRS10 case temperature
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Scott Mace via time-nuts
2018-11-16 20:36:39 UTC
Permalink
I have been experimenting with a PRS10 and using Lady Heather to collect data. This unit had several failed components in the lamp
assembly, which I replaced and the unit locks well now. One thing I noticed is that on cold startup, the unit seems to think it's
already at 40-50C, when in reality it's only slightly above room temperature. The sensor settles around 79-82C. I've measured the
baseplate and it is around 50C. I believe that all of the ovens are running slightly low as a result (if I understand the circuit
correctly). I'm thinking that the case temp sensor, a LM45C, on the power supply board is bad. Anyone else running a PRS10 with
reasonably correct baseplate temperatures?

Here are some of the numbers I'm seeing:

AD1 - Heater supply : 24.360V
AD2 - +24V supply: 24.370V
AD3 - Lamp FET drain: 4.910V
AD4 - Lamp FET gate: 4.080V
AD5 - OCXO heater: 1.811V
AD6 - Cell heater: 2.101V
AD7 - Lamp heater: 1.513V
AD8 - Photo signal: 3.831
AD9 - I/V converter: 4.804V
AD10 - Case temperature: 80.80 C
^^^^
AD11 - XTAL thermistors: 0.961
AD12 - Cell thermistors: 0.971
AD13 - Lamp thermistors: 0.972
AD14 - Freq cal pot: 2.337
AD15 - Analog ground: 0.005V
AD16 - TXCO varactor: 7.240V
AD17 - VCO varactor: 11.520V
AD18 - Multiplier gain: 11.520V
AD19 - RF synth lock: 4.900V



Scott
Mark Sims
2018-11-16 21:48:03 UTC
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My case temp runs around 70C with the SRS heatsink installed. If you don't have a heatsink (a rather bad idea) it might run 80C. The latest SRS heatsinks don't seem to be as good as the earlier units which had a lot more metal to them... my heatsink is the later model.
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Dana Whitlow
2018-11-16 23:50:27 UTC
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My PRS-10 (a telecom version) runs with a heatsink temp of around 55C of
a bit less. But some areas of the case actually run a few deg hotter than
that.

Dana
Post by Mark Sims
My case temp runs around 70C with the SRS heatsink installed. If you
don't have a heatsink (a rather bad idea) it might run 80C. The latest SRS
heatsinks don't seem to be as good as the earlier units which had a lot
more metal to them... my heatsink is the later model.
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Scott Mace via time-nuts
2018-11-17 00:01:54 UTC
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I placed a large fan in front of the heat sink and it only cooled it down to 69C according to the case temp sensor. There's no way
the case is actually anywhere close to that temp, it's maybe 40C with that fan running. I'll replace the LM45C and see what happens.

Scott
Post by Dana Whitlow
My PRS-10 (a telecom version) runs with a heatsink temp of around 55C of
a bit less. But some areas of the case actually run a few deg hotter than
that.
Dana
Post by Mark Sims
My case temp runs around 70C with the SRS heatsink installed. If you
don't have a heatsink (a rather bad idea) it might run 80C. The latest SRS
heatsinks don't seem to be as good as the earlier units which had a lot
more metal to them... my heatsink is the later model.
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Shaun Merrigan
2018-11-16 22:02:02 UTC
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Scott:

Here are the analog output values I am seeing:

ad0 0.005 Spare
ad1 2.316 +24 Volt Heater Supply
ad2 2.327 +24 Volt Electronics Supply
ad3 0.491 Lamp Drain Voltage
ad4 0.343 Lamp Gate Voltage
ad5 2.402 Crystal Heater Control
ad6 2.358 Cell Heater Control
ad7 1.557 Lamp Heater Control
ad8 2.413 AC Photosignal
ad9 2.491 Photocell I/V Voltage
ad10 0.657 Case Temperature
ad11 0.950 Crystal Thermistors
ad12 0.958 Cell Thermistors
ad13 0.957 Lamp Thermistors
ad14 2.503 Frequency Pot Voltage
ad15 0.005 Analog Ground
ad16 2.520 22.48MHz Varactor Voltage
ad17 3.190 360MHz Varactor Voltage
ad18 1.910 Gain Control Voltage
ad19 4.740 RF Synthesizer Lock Indicator

This unit has a large passive heatsink and the values are from RbMon.

Shaun Merrigan

-----Original Message-----
From: time-nuts <time-nuts-***@lists.febo.com> On Behalf Of Scott Mace via time-nuts
Sent: Friday, November 16, 2018 1:37 PM
To: time-***@lists.febo.com
Cc: Scott Mace <***@intt.net>
Subject: [time-nuts] PRS10 case temperature

I have been experimenting with a PRS10 and using Lady Heather to collect data. This unit had several failed components in the lamp assembly, which I replaced and the unit locks well now. One thing I noticed is that on cold startup, the unit seems to think it's already at 40-50C, when in reality it's only slightly above room temperature. The sensor settles around 79-82C. I've measured the baseplate and it is around 50C. I believe that all of the ovens are running slightly low as a result (if I understand the circuit correctly). I'm thinking that the case temp sensor, a LM45C, on the power supply board is bad. Anyone else running a PRS10 with reasonably correct baseplate temperatures?

Here are some of the numbers I'm seeing:

AD1 - Heater supply : 24.360V
AD2 - +24V supply: 24.370V
AD3 - Lamp FET drain: 4.910V
AD4 - Lamp FET gate: 4.080V
AD5 - OCXO heater: 1.811V
AD6 - Cell heater: 2.101V
AD7 - Lamp heater: 1.513V
AD8 - Photo signal: 3.831
AD9 - I/V converter: 4.804V
AD10 - Case temperature: 80.80 C
^^^^
AD11 - XTAL thermistors: 0.961
AD12 - Cell thermistors: 0.971
AD13 - Lamp thermistors: 0.972
AD14 - Freq cal pot: 2.337
AD15 - Analog ground: 0.005V
AD16 - TXCO varactor: 7.240V
AD17 - VCO varactor: 11.520V
AD18 - Multiplier gain: 11.520V
AD19 - RF synth lock: 4.900V



Scott

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Mark Sims
2018-11-17 02:48:22 UTC
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The case temperature derived from the ADC reading does not match actual measured values. The PRS10 data sheet says it is roughly the temperature midway between the baseplate and lamp temps.
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Scott Mace via time-nuts
2018-11-17 04:41:30 UTC
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I think I figured out the problem. When I rebuilt the lamp assembly, the R901 air heater resistor was listed as a 750ohm 2W on the
schematic so that's what I installed. I just measured the old resistor, which had a broken lead, and it is 534ohms. I sort of
repaired the broken lead and installed it. Now the unit locks up real quick and the AD10 sensor is showing around 70C. The other
problems were a broken C904 and a bad U800 8V regulator.

Scott
Post by Mark Sims
The case temperature derived from the ADC reading does not match actual measured values. The PRS10 data sheet says it is roughly the temperature midway between the baseplate and lamp temps.
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Chris Burford
2018-11-17 02:43:25 UTC
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I see a 42C baseplate temp on my PRS10. I have the newer (U-shaped) heatsink attached. I also have a 70mm fan moving air at a low speed across the the long axis of the heatsink.

The case temp (ad10) as seen by RbMon is generally 67.2C

Chris
Post by Scott Mace via time-nuts
I have been experimenting with a PRS10 and using Lady Heather to collect data. This unit had several failed components in the lamp
assembly, which I replaced and the unit locks well now. One thing I noticed is that on cold startup, the unit seems to think it's
already at 40-50C, when in reality it's only slightly above room temperature. The sensor settles around 79-82C. I've measured the
baseplate and it is around 50C. I believe that all of the ovens are running slightly low as a result (if I understand the circuit
correctly). I'm thinking that the case temp sensor, a LM45C, on the power supply board is bad. Anyone else running a PRS10 with
reasonably correct baseplate temperatures?
AD1 - Heater supply : 24.360V
AD2 - +24V supply: 24.370V
AD3 - Lamp FET drain: 4.910V
AD4 - Lamp FET gate: 4.080V
AD5 - OCXO heater: 1.811V
AD6 - Cell heater: 2.101V
AD7 - Lamp heater: 1.513V
AD8 - Photo signal: 3.831
AD9 - I/V converter: 4.804V
AD10 - Case temperature: 80.80 C
^^^^
AD11 - XTAL thermistors: 0.961
AD12 - Cell thermistors: 0.971
AD13 - Lamp thermistors: 0.972
AD14 - Freq cal pot: 2.337
AD15 - Analog ground: 0.005V
AD16 - TXCO varactor: 7.240V
AD17 - VCO varactor: 11.520V
AD18 - Multiplier gain: 11.520V
AD19 - RF synth lock: 4.900V
Scott
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