开云体育

Faulty ATU 100 EXT

g4edg #929 Hi Ive just been given a faulty ATU 100 EXT (brand new ready built unit). The display remained dark on powering up, I happened to have a spare display so replaced it which resulted in a nice bright display. Test mode performs as expected, L and C can be adjusted up and down by the AUTO/BYPASS buttons.? When I try to get the tuner to autotune the tuner refuses to react. I noticed that the power indicated on the display, showing only 0.2w even when driven with 50w from my transceiver.? I have measured the voltage derived from the coupler when driven with 50w...around 1v on the forward diode, by the time this reaches pins 2 and 3 on the processor this is down to a few tens of millivolts. I wonder if anyone has measured these voltages?? It would seem the power detected by the processor is deemed too low to perform the tuning action at 0.2w Any thoughts? 73 Steve G4EDG
Onno PA1AP All Messages By This Member #930 I'm not sure which pic controller is placed on the system but depending type the maximum input is between 4 and 5 volt for full power. Looks to me something not correct with the bridge or components between bridge and adc pin of the pic.? Best regards Onno Op zo 28 nov. 2021 20:24 schreef g4edg via <G4edg=[email protected]>: toggle quoted message Show quoted text Hi Ive just been given a faulty ATU 100 EXT (brand new ready built unit). The display remained dark on powering up, I happened to have a spare display so replaced it which resulted in a nice bright display. Test mode performs as expected, L and C can be adjusted up and down by the AUTO/BYPASS buttons.? When I try to get the tuner to autotune the tuner refuses to react. I noticed that the power indicated on the display, showing only 0.2w even when driven with 50w from my transceiver.? I have measured the voltage derived from the coupler when driven with 50w...around 1v on the forward diode, by the time this reaches pins 2 and 3 on the processor this is down to a few tens of millivolts. I wonder if anyone has measured these voltages?? It would seem the power detected by the processor is deemed too low to perform the tuning action at 0.2w Any thoughts? 73 Steve G4EDG
Tim Ostley All Messages By This Member #931 开云体育 Steve, Try tuning it with 5W. If it works then you need to reduce the number of turns on the sense transformer from 10 to 5 and change the settings in the eprom (needs a pic programmer) so that it works for QRP. Best 73 Tim M0CZP toggle quoted message Show quoted text On 28 Nov 2021, at 19:17, g4edg via <G4edg@...> wrote: Hi Ive just been given a faulty ATU 100 EXT (brand new ready built unit). The display remained dark on powering up, I happened to have a spare display so replaced it which resulted in a nice bright display. Test mode performs as expected, L and C can be adjusted up and down by the AUTO/BYPASS buttons.? When I try to get the tuner to autotune the tuner refuses to react. I noticed that the power indicated on the display, showing only 0.2w even when driven with 50w from my transceiver.? I have measured the voltage derived from the coupler when driven with 50w...around 1v on the forward diode, by the time this reaches pins 2 and 3 on the processor this is down to a few tens of millivolts. I wonder if anyone has measured these voltages?? It would seem the power detected by the processor is deemed too low to perform the tuning action at 0.2w Any thoughts? 73 Steve G4EDG
[email protected] All Messages By This Member #932 Auto tuning with 50w should not be a problem. It should work and it should read something close to the 50. Regardless of whether this is a PIC that has a 4 or 5 volt reference. I think these devices mostly use the version with a 4.096 Volt reference. I believe the maximum power the design? can read is roughly 150W so extrapolating a bit the voltage you are seeing is too low to represent your power level. I would be looking at the bridge peak detector diodes or their filter capacitors. Not very likely to be an associated resistor voltage divider unless the thing got hit with a over power situation and was damaged. Guessing the diodes blow out first. I think you can remove the diode and check with a scope that you have the sampling voltage at the 10 turn coil and then figure which peak detector component is bad. I would check the detector diode pretty carefully. I think the series resistor and the voltage divider likely go a long way to protect the PIC underr bad circumstances. regards, john
Glenn All Messages By This Member #933 Steve If you trace through the schematic you will see the forward and reverse voltages from the SWR diodes are fed to the PIC via a voltage divider using 68k and 34k resistors.. If you trace through it would seem to be there is a short on the line close to the PIC input effectively across the 34k resistor.. vk3pe toggle quoted message Show quoted text On Mon, Nov 29, 2021 at 06:24 AM, g4edg wrote: Hi Ive just been given a faulty ATU 100 EXT (brand new ready built unit). The display remained dark on powering up, I happened to have a spare display so replaced it which resulted in a nice bright display. Test mode performs as expected, L and C can be adjusted up and down by the AUTO/BYPASS buttons.? When I try to get the tuner to autotune the tuner refuses to react. I noticed that the power indicated on the display, showing only 0.2w even when driven with 50w from my transceiver.? I have measured the voltage derived from the coupler when driven with 50w...around 1v on the forward diode, by the time this reaches pins 2 and 3 on the processor this is down to a few tens of millivolts. I wonder if anyone has measured these voltages?? It would seem the power detected by the processor is deemed too low to perform the tuning action at 0.2w Any thoughts? 73 Steve G4EDG
Glenn All Messages By This Member #934 开云体育 John He quotes 1v out of the SWR diode detector but nothing at the PIC. glenn
g4edg #935 Hi Thanks to you all for your input on this problem, I think the general consensus is the voltages arriving at the PIC inputs from the bridge are too low for some reason.? I'll rebuild the bridge circuit...maybe the windings are not in the correct sense...if that matters and check the diodes.... though they do show 0.2v on the diode check facility of my multimeter which seems about right for a schotkey diode, along with the 34k and 68k resistors and decoupling caps. I would just like to ask, in bypass mode does the display show approximately the right power level and SWR ....at 50w from my IC7300 mine shows 0.2w I'll check and rebuild the bridge circuit and let you know the outcome. If you could let me know how your display reacts in bypass mode that would be great. Thanks again Steve G4EDG ?
Onno PA1AP All Messages By This Member #936 The bridge does not change when in bypass mode. It's always inline.? The firmware does read the voltages from the bridge independent of tuner mode / setting. So indeed, when in bypass you should see the power as well swr indication. Regards Onno Op ma 29 nov. 2021 15:37 schreef g4edg via <G4edg=[email protected]>: toggle quoted message Show quoted text Hi Thanks to you all for your input on this problem, I think the general consensus is the voltages arriving at the PIC inputs from the bridge are too low for some reason.? I'll rebuild the bridge circuit...maybe the windings are not in the correct sense...if that matters and check the diodes.... though they do show 0.2v on the diode check facility of my multimeter which seems about right for a schotkey diode, along with the 34k and 68k resistors and decoupling caps. I would just like to ask, in bypass mode does the display show approximately the right power level and SWR ....at 50w from my IC7300 mine shows 0.2w I'll check and rebuild the bridge circuit and let you know the outcome. If you could let me know how your display reacts in bypass mode that would be great. Thanks again Steve G4EDG ?
[email protected] All Messages By This Member #937 Yea, Sorry. I read too fast. I thoughyt he said 0.2v and it was 0,2w.so it could be a problem with a pc board trace for sure. John
Tim Ostley All Messages By This Member #938 开云体育 Nope, the standard shipped hardware / software needs 5w min to tune. If you rewind the bridge and change the settings it will fund on about 1w. It won’t tune on .2w at all? Tim M0CZP toggle quoted message Show quoted text On 29 Nov 2021, at 16:26, john_mellars via groups.io <john_mellars@...> wrote: ?Yea, Sorry. I read too fast. I thoughyt he said 0.2v and it was 0,2w.so it could be a problem with a pc board trace for sure. John
g4edg #963 Hi Finally have this faulty ATU-100 repaired... and what a mess it was! The following is offered in the hope it will save others some time and energy. The original fault symptoms which seemed to originate in the SWR detector bridge was due to a subtle disconnection in one of the sense windings which was resolved by rewinding the whole bridge. The ATU would still not tune reliability, if I touched the output of the bridge with a multimeter probe the ATU tuned after a fashion. It appears the SMD caps C18 and C19 are either faulty or too low in value to decouple the bridge output. I replaced them with the only SMD caps I had to hand, 223's which seemed to do the job. The tuner still did not tune properly, I used a NanoVNA to connected to the RF IN connector to establish that the capacitors C1 to C7 were not being selected in increasing order (using the tuner in TEST MODE) Briefly the faults were as follows. C6 470pf burned up on applying RF C3 47pf? cracked and open circuit C7 1000pf cracked and open circuit Q9 faulty and not operating relay S12 to select C4 100pf C7 not being connected when the relay S15 operated due to a missing plated through hole...replaced by a wire. Combine this with the original faulty display and wires continually breaking off the front panel switches, it was a bit of a Friday afternoon job...literally! A pretty poor show for a ready built unit. I wonder if anybody has a source of the 47, 470 and 1000pf caps (silver mica 500v low loss)? I'm just using some regular small caps until I can find some replacements. 73 Steve G4EDG ? ?

Previous Topic Next Topic