Carlton dehumidifier dh-100 interference. - UK Vintage Radio Repair and Restoration Discussion Forum

Gi4CZW Cliff · 4th Mar 2020, 12:25 pm

My dehumidifier was causing interference ( clicking noise on radio ) and I noticed that it was rocking about on it's castors in rythm to to the clicking. So to have a look inside. Lots of screws to consider, yet I don't want to undo the wrong ones. Anybody know how it's done.
Cliff.

Techman · 4th Mar 2020, 1:16 pm

I've got a couple of old (must be over 30 years old) dehumidifiers (not the same make as yours) and on the odd occasion when I've had to dismantle them I've found that there are 'many' screws to remove, some of which are different thicknesses and lengths. I think you'll just have to use logic, common sense and take your time and note where everything goes as you take it apart and do the same on reassembly.

Gi4CZW Cliff · 4th Mar 2020, 4:25 pm

Hello Techman, thank you for that. So I take out lots of screws, spill some water, take the back panel off, put some screws back in. A look around shows nothing and switch-on shows nothing wrong ? Have it running near to me now, keeping an eye on it. As it was on carpet earlier and it's of the drip into an internal bucket type, with a float to switch-off when full. I'm thinking if the bucket was not correctly located then the switch and swaying motion may have been the problem.
thanks,
Cliff.

Techman · 4th Mar 2020, 7:41 pm

I looked at an on-line picture of your type and it looks similar to mine. You shouldn't get water spillage as you'd let it sit for a short while before removing and emptying the tank. Dismantling is a lot more involved than just taking the back off, so I'd leave it alone if you don't have to do it. There's no instructional manuals available for these that I know of, so you just have to follow your nose and use common sense. Most of the problems are caused by the tank not being properly inserted, so if in doubt, pull it out and re-insert...as you've probably just found out.

Gi4CZW Cliff · 5th Mar 2020, 3:27 pm

Not fixed yet. Unit still starting/stopping rhythmicly. Seems to be the PCB, as from diagram other component not concerned, white plug goes to sensor down at chiller pipes and shows 10K Ohms ( substituting higher or lower has no effect). Touching the relay, I detect that it is operating/releasing to the rhythm.
Any thoughts as to what the PCB does ?
Cliff.

CambridgeWorks · 5th Mar 2020, 4:00 pm

Firstly, that relay cycling on off will overload the compressor if there is not a 2 or 3 minute gap to allow the cylinder head pressure to reduce. There is a protecive thermal electric cutout goes to C (common) of the compressor to offer some protection from burning out. Do not tempt fate by leaving it as it is for testing.
Assuming you are ok working on this safely, my first step would be trace out the psu part of the pcb. Looks like a capacitor dropper, feeding a half wave rectifier and the black electrolytic smoothing cap. I would check the ac voltage input to the diode and see if the dc side looks ok. If down, I would replace the electrolytic which i assume is a smoothing capacitor straight after the diode rectifier. Could be low in value and not allowing enough dc supply for the relay and rest of the circuit. Relay looks might be 24V?? If so, expect about 24V or a bit more as smoothed dc. I also note there is a zener, zd1, which i would assume is for the ic supply? What uf and voltage is the electrolytic?
Take great care in doing all of this!
Rob

Techman · 5th Mar 2020, 4:21 pm

That's a lot more modern than mine. No printed circuits in mine, it's all electro-mechanical. Capacitors used as droppers are notorious for failure in this type of appliance.

CambridgeWorks · 5th Mar 2020, 7:20 pm

"Capacitors used as droppers are notorious for failure in this type of appliance."

I have been lucky then. Never seen that. My last experience was my aircon system control pcb. Don't recall it having a bulge or any visible signs, just was useless as a high value electrolytic.
At least Cliff has another idea as to just what to check. Thanks Techman.
Rob

buggies · 5th Mar 2020, 7:48 pm

I would check the capacitance of the yellow caps - one of them will likely be the "dropper" and the capacitance will have dropped...
I have repaired a number of household electrical items which have suffered intermittent operation due to insufficient current being available due to X rated capacitance reduction.

dryjoint · 5th Mar 2020, 9:39 pm

Just a thought based on a problem I had with a paper shredder with a similar power supply approach, check any resistor(s) in series with the "dropper" capacitor. The two 100 ohm ones (R2 and R3) look favourite to me. The resistor in my unit was o/c but if there is one in your dehumidifier it may have crept up in value.

Gi4CZW Cliff · 5th Mar 2020, 9:51 pm

Hello again and thank you for the pointers. Drawing out the power part of the circuit now and will be testing the components mentioned tomorrow. Cliff.

Gi4CZW Cliff · 6th Mar 2020, 2:28 pm

You are correct, power for relay and chip is-- Live, X2 cap, 50 Ohms and diodes to Neutral--. The twin 100 Ohms are testing 50, that big cap is marked " 0.68uF X2 250V~/275V~GMF " when I have it off the pcb it tests 0.41uF. The X2 across L and N is marked " 0.1 uF (K) X2 250V~/275V~ " and measures 0.05uF.
The black electroletic is marked 100uF35V and tests 95uF. The other yellow is marked 0.068uF and when out tests 0.06nF (yes nano). Titchy one not tested.
Not sure where to source four cap's in ones.
Cliff.

buggies · 6th Mar 2020, 7:30 pm

Personal view only - I would not bother with changing the X2 across the mains - as it should not affect operation of the dehumidifier but could let some interference out.
The .68uF reading .41uF would, I guess, limit the current to 60% of the original design so would be my first suspect - possibly tacking .22uF across it as a quick test.
Dunno what the .06nF is supposed to do.

Gi4CZW Cliff · 7th Mar 2020, 12:22 pm

Hello George, the low 0.068uF at 0.41 looks like the fault. The 0.068uF ( now 0.06nF ) is in series with the 100 Ohm beside it and connects Live to Comp, so spark suppression ? Replacements on order.
Cliff.

Gi4CZW Cliff · 11th Mar 2020, 8:54 pm

Update. Components arrived, fitted and unit now running as it should.
Many thanks to Techman for encouragement to open up the unit and get inside, robinshack for incentive to trace out the circuit and what to expect. Also buggies and dryjoint to keep me interested. As I have not done quite that sort of repair before it was good to have you around.
thanks again,
Cliff.

4th Mar 2020, 12:25 pm	#1
Gi4CZW Cliff Pentode Join Date: May 2011 Location: Enniskillen, Fermanagh, UK. Posts: 188	Carlton dehumidifier dh-100 interference. My dehumidifier was causing interference ( clicking noise on radio ) and I noticed that it was rocking about on it's castors in rythm to to the clicking. So to have a look inside. Lots of screws to consider, yet I don't want to undo the wrong ones. Anybody know how it's done. Cliff.

4th Mar 2020, 1:16 pm	#2
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Re: Carlton dehumidifier dh-100 interference. I've got a couple of old (must be over 30 years old) dehumidifiers (not the same make as yours) and on the odd occasion when I've had to dismantle them I've found that there are 'many' screws to remove, some of which are different thicknesses and lengths. I think you'll just have to use logic, common sense and take your time and note where everything goes as you take it apart and do the same on reassembly.

4th Mar 2020, 4:25 pm	#3
Gi4CZW Cliff Pentode Join Date: May 2011 Location: Enniskillen, Fermanagh, UK. Posts: 188	Re: Carlton dehumidifier dh-100 interference. Hello Techman, thank you for that. So I take out lots of screws, spill some water, take the back panel off, put some screws back in. A look around shows nothing and switch-on shows nothing wrong ? Have it running near to me now, keeping an eye on it. As it was on carpet earlier and it's of the drip into an internal bucket type, with a float to switch-off when full. I'm thinking if the bucket was not correctly located then the switch and swaying motion may have been the problem. thanks, Cliff.

4th Mar 2020, 7:41 pm	#4
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Re: Carlton dehumidifier dh-100 interference. I looked at an on-line picture of your type and it looks similar to mine. You shouldn't get water spillage as you'd let it sit for a short while before removing and emptying the tank. Dismantling is a lot more involved than just taking the back off, so I'd leave it alone if you don't have to do it. There's no instructional manuals available for these that I know of, so you just have to follow your nose and use common sense. Most of the problems are caused by the tank not being properly inserted, so if in doubt, pull it out and re-insert...as you've probably just found out.

5th Mar 2020, 3:27 pm	#5
Gi4CZW Cliff Pentode Join Date: May 2011 Location: Enniskillen, Fermanagh, UK. Posts: 188	Re: Carlton dehumidifier dh-100 interference. Not fixed yet. Unit still starting/stopping rhythmicly. Seems to be the PCB, as from diagram other component not concerned, white plug goes to sensor down at chiller pipes and shows 10K Ohms ( substituting higher or lower has no effect). Touching the relay, I detect that it is operating/releasing to the rhythm. Any thoughts as to what the PCB does ? Cliff. Attached Thumbnails

5th Mar 2020, 4:00 pm	#6
CambridgeWorks Nonode Join Date: Jun 2010 Location: Spalding, Peterborough, Cambridgeshire, UK. Posts: 2,858	Re: Carlton dehumidifier dh-100 interference. Firstly, that relay cycling on off will overload the compressor if there is not a 2 or 3 minute gap to allow the cylinder head pressure to reduce. There is a protecive thermal electric cutout goes to C (common) of the compressor to offer some protection from burning out. Do not tempt fate by leaving it as it is for testing. Assuming you are ok working on this safely, my first step would be trace out the psu part of the pcb. Looks like a capacitor dropper, feeding a half wave rectifier and the black electrolytic smoothing cap. I would check the ac voltage input to the diode and see if the dc side looks ok. If down, I would replace the electrolytic which i assume is a smoothing capacitor straight after the diode rectifier. Could be low in value and not allowing enough dc supply for the relay and rest of the circuit. Relay looks might be 24V?? If so, expect about 24V or a bit more as smoothed dc. I also note there is a zener, zd1, which i would assume is for the ic supply? What uf and voltage is the electrolytic? Take great care in doing all of this! Rob __________________ Apprehension creeping like a tube train up your spine - Cymbaline. Film More soundtrack - Pink Floyd

5th Mar 2020, 4:21 pm	#7
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Re: Carlton dehumidifier dh-100 interference. That's a lot more modern than mine. No printed circuits in mine, it's all electro-mechanical. Capacitors used as droppers are notorious for failure in this type of appliance.

5th Mar 2020, 7:20 pm	#8
CambridgeWorks Nonode Join Date: Jun 2010 Location: Spalding, Peterborough, Cambridgeshire, UK. Posts: 2,858	Re: Carlton dehumidifier dh-100 interference. "Capacitors used as droppers are notorious for failure in this type of appliance." I have been lucky then. Never seen that. My last experience was my aircon system control pcb. Don't recall it having a bulge or any visible signs, just was useless as a high value electrolytic. At least Cliff has another idea as to just what to check. Thanks Techman. Rob __________________ Apprehension creeping like a tube train up your spine - Cymbaline. Film More soundtrack - Pink Floyd

5th Mar 2020, 7:48 pm	#9
buggies Heptode Join Date: Jan 2009 Location: West Lothian, UK. Posts: 761	Re: Carlton dehumidifier dh-100 interference. I would check the capacitance of the yellow caps - one of them will likely be the "dropper" and the capacitance will have dropped... I have repaired a number of household electrical items which have suffered intermittent operation due to insufficient current being available due to X rated capacitance reduction. __________________ George

5th Mar 2020, 9:39 pm	#10
dryjoint Tetrode Join Date: Nov 2009 Location: Southend-on-Sea, Essex, UK. Posts: 60	Re: Carlton dehumidifier dh-100 interference. Just a thought based on a problem I had with a paper shredder with a similar power supply approach, check any resistor(s) in series with the "dropper" capacitor. The two 100 ohm ones (R2 and R3) look favourite to me. The resistor in my unit was o/c but if there is one in your dehumidifier it may have crept up in value.

5th Mar 2020, 9:51 pm	#11
Gi4CZW Cliff Pentode Join Date: May 2011 Location: Enniskillen, Fermanagh, UK. Posts: 188	Re: Carlton dehumidifier dh-100 interference. Hello again and thank you for the pointers. Drawing out the power part of the circuit now and will be testing the components mentioned tomorrow. Cliff.

6th Mar 2020, 2:28 pm	#12
Gi4CZW Cliff Pentode Join Date: May 2011 Location: Enniskillen, Fermanagh, UK. Posts: 188	Re: Carlton dehumidifier dh-100 interference. You are correct, power for relay and chip is-- Live, X2 cap, 50 Ohms and diodes to Neutral--. The twin 100 Ohms are testing 50, that big cap is marked " 0.68uF X2 250V~/275V~GMF " when I have it off the pcb it tests 0.41uF. The X2 across L and N is marked " 0.1 uF (K) X2 250V~/275V~ " and measures 0.05uF. The black electroletic is marked 100uF35V and tests 95uF. The other yellow is marked 0.068uF and when out tests 0.06nF (yes nano). Titchy one not tested. Not sure where to source four cap's in ones. Cliff.

6th Mar 2020, 7:30 pm	#13
buggies Heptode Join Date: Jan 2009 Location: West Lothian, UK. Posts: 761	Re: Carlton dehumidifier dh-100 interference. Personal view only - I would not bother with changing the X2 across the mains - as it should not affect operation of the dehumidifier but could let some interference out. The .68uF reading .41uF would, I guess, limit the current to 60% of the original design so would be my first suspect - possibly tacking .22uF across it as a quick test. Dunno what the .06nF is supposed to do. __________________ George

7th Mar 2020, 12:22 pm	#14
Gi4CZW Cliff Pentode Join Date: May 2011 Location: Enniskillen, Fermanagh, UK. Posts: 188	Re: Carlton dehumidifier dh-100 interference. Hello George, the low 0.068uF at 0.41 looks like the fault. The 0.068uF ( now 0.06nF ) is in series with the 100 Ohm beside it and connects Live to Comp, so spark suppression ? Replacements on order. Cliff.

11th Mar 2020, 8:54 pm	#15
Gi4CZW Cliff Pentode Join Date: May 2011 Location: Enniskillen, Fermanagh, UK. Posts: 188	Re: Carlton dehumidifier dh-100 interference. Update. Components arrived, fitted and unit now running as it should. Many thanks to Techman for encouragement to open up the unit and get inside, robinshack for incentive to trace out the circuit and what to expect. Also buggies and dryjoint to keep me interested. As I have not done quite that sort of repair before it was good to have you around. thanks again, Cliff.