Sherwood RD-6108 receiver turns on and off randomly.

[Chuck]

I don't have a service manual for this receiver but I checked the 6V
standby voltage and the 15V line from the standby power supply and
they both are at the correct voltage and have low ripple. I've heated
and cooled the boards with no change of symptoms. The problem began by
the receiver turning on in the middle of the night. Reset the micro
but it happened again 2 hours later. Now it clicks off when on from
anywhere from 2 seconds to hours. Is there a common fault for this
receiver causing these symptoms? Thanks. Chuck

[peterw...@gmail.com]

Silly suggestion - does a piece of black tape over the IR sensor help at all? I suggest because I am seeing lots of "smart house" stuff starting to interfere with some legacy equipment out there. You might also isolate the remote as some of the touch-pad contacts may be aging and making random contact. That is to get past the obvious.

Otherwise, I would trace out the on/off circuit and look for a bad capacitor on in that lot. This unit is approaching 18 years old, or so, about the time these tiny little electrolytics start to fail.

Best of luck with it!

[Dave Platt]

Check for current leakage in the areas around the on/off switch.

Some decades ago I had a Macintosh II which had a habit of turning
itself on without human intervention - usually in the morning.

I eventually traced the problem to the keyboard. The Mac II uses a
"soft" power switching setup, where the keyboard power switch pulls
one of the ADB-cable lines down to ground. This sense line has a very
high source impedance, and it didn't take much current leakage to
ground to false-trigger it.

The Mac II was in a spare bedroom that got quite cold at night during
the winter (the place we were renting had a lousy heating system and
no insulation). In the morning, my wife would take a shower, humid
air would flood the back of the house, some moisture would condense
inside the cold keyboard case, and a few microamps of current would
leak across the switch contacts. BONG!

I cleaned the keyboard's PC board in the area of the switch with some
alcohol, coated it with something insulating (I think I used a thin
film of my wife's acrylic nail polish) and the problem went away.

So, I'd suggest inspecting the power switch and the PC board around
it. Possibly some old flux, or the dreaded "yellow glue" on the board
has become conductive with age. Clean it all up thoroughly (careful
scraping, flux-remover spray, etc.), dry well, and apply a conformal
insulation coating of some sort, and see if that resolves the problem.

Looking at the manual for the RD-6106 (which may be similar) - this
receiver does seem to have a "soft" power switching system, where the
main AC voltage can be controlled by both a "hard" switch, and by a
relay system driven from the control logic. The control logic then
looks at a "standby" pushbutton... this is a low-level contact closure
and seems to be tied in with the main keyboard scanning logic. So, a
contaminated "standby" PC board / assembly might be at fault.

[Chuck]

Thank you for your input. I had removed the conductive glue from the
boards with no improvement. I've seen the leaky tact switch faults on
tvs, but I didn't think of it in this case. Will disconnect it and see
if the receiver stays on.

[Chuck]

Yes, I covered the IR window but I didn't disconnect the IR receiver
which have caused weird tv symptoms. Thank you for your suggestions.

[Chuck H.]

On Mon, 17 Sep 2018 11:30:08 -0700, dpl...@coop.radagast.org (Dave
Platt) wrote:

David,
As you surmised, the problem was the power tact switch. I didn't check
it because I heard a weird distortion while playing a cd the night
before. So I thought the problem was a voltage inbalance causing the
protection circuit to engage. The last unit I repaired was a
dehumidifier where every tact switch was open so luckily I had the
switch in stock. Years ago a high end Technics cassette deck came into
the shop. Every tact switch was open so I asked the customer what
environment the unit was used in. It was used in a room where metal
was etched. The fumes ate away the tact switches' internals. Thanks
for guiding me in the right direction.

[jurb...@gmail.com]

>"The last unit I repaired was a
dehumidifier where every tact switch was open"

So dehumidifiers are fucking digital now ? What is next, bath towels ?

(it took me a while to think of something, can't use chairs, toilets, vacuum cleaners, lawnmowers, refrigerators, flashlights, toasters, sinks, bathtubs, ummm, what else can you use ?)

[tabb...@gmail.com]

On Thursday, 20 September 2018 07:27:41 UTC+1, jurb...@gmail.com wrote:

> >"The last unit I repaired was a
> dehumidifier where every tact switch was open"
>
> So dehumidifiers are fucking digital now ? What is next, bath towels ?

electronically controlled units work much better than mechanical humidistats

> (it took me a while to think of something, can't use chairs, toilets, vacuum cleaners, lawnmowers, refrigerators, flashlights, toasters, sinks, bathtubs, ummm, what else can you use ?)

should I ask why you can't use any of those?


NT

[Tim R]

On Wednesday, September 19, 2018 at 5:16:35 PM UTC-4, Chuck H. wrote:
> David,
> As you surmised, the problem was the power tact switch. I didn't check
> it because

Even though I know better, I have screwed diagnosis many times by thinking I knew what the problem might be and going down the wrong path. It's almost irresistible sometimes.

[John-Del]

On Thursday, September 20, 2018 at 6:08:27 AM UTC-4, tabb...@gmail.com wrote:
> On Thursday, 20 September 2018 07:27:41 UTC+1, jurb...@gmail.com wrote:
>
> > >"The last unit I repaired was a
> > dehumidifier where every tact switch was open"
> >
> > So dehumidifiers are fucking digital now ? What is next, bath towels ?
>
> electronically controlled units work much better than mechanical humidistats
>

If you need to keep humidity to within a fraction of a percent perhaps, but in my experience, electronic controls add complexity and complexity means trouble.

If this dehumidifier was used to keep someone's basement dry and sweet smelling, it would be far better off with a quality mechanical humidistat that kept the humidity within a few points either way. As it is, the poster mentioned that this needed tact switches, something a mechanical unit wouldn't have.

[Chuck]

On Thu, 20 Sep 2018 07:11:02 -0700 (PDT), Tim R <timot...@aol.com>
wrote:

You bet. I spent 47 years repairing consumer , pro audio, television
studio, video conferencing, and server equipment. Though retired, I
shouldn't have slipped this much.

[jurb...@gmail.com]

>"electronically controlled units work much better than mechanical humidistats "

Until they break. A mechanical one has a strand of soemthing in it that can be replaced, the spring can be cut down or stretched to adjust if it changes over time. The corroded wires can be replaced.

If the chip goes bad and it has a number on it like XD333YTOT23AAA1902**/A to buy a whole new dehumidifier and throw that one in the dumpster, Freon and all.

And they probably get a fucking energy star compliance certification. And your money went to a country that uses predatory trade practices. And the landfills fill up until this country is nothing but a landfill.

But it's more important to hold it between 71 and 75 % because 69 and 77 % would be totally unacceptable.

Right.

That's not Luddite, that's green and it is actually conservative, like to conserve.

[jurb...@gmail.com]

>"should I ask why you can't use any of those? "

Look, ICs are wonderful and should be used wherever they are needed. Now you want your food to spoil because some static electricity got into the works somehow ? Would you like to pay to rebuild a water valve, possibly fifty bucks if they even did that, instead of replacing a 5 cent washer ? How about people who wipe their ass after they stand up and the toilet goes kawoosh and they have to sit down to make it flush AGAIN to get the paper down " That really saves water, right ?

How about cars that can be hacked into and the hacker can control the brakes and even possibly the steering ? (it has been done but not the steering yet as far as I know) How about people using shodan and looking in on your baby monitor ? Or gaining control over your furnace and microwave, maybe a few other things like your home security system ?

I think it is great that you can see your security cameras on your phone, but to be able to disable the system ? How about a phone call and just give them the damn code ?

[mako...@yahoo.com]

How about people who wipe their ass after they stand up and the toilet goes kawoosh and they have to sit down to make it flush AGAIN to get the paper down

lol

when the poster asked what next will be digital.....

as a joke i was thinking "toilet paper'

but you are right....they already did that!

m

[tabb...@gmail.com]

On Thursday, 20 September 2018 15:21:04 UTC+1, John-Del wrote:

but what you describe is not the options. Mechanical humidistats are dire in terms of RH control, and not long term reliable. Electronics are accurate and at least some survive long term. I far prefer bimetal thermostats for general heating use, but humidistats are quite a different animal.


NT

[tabb...@gmail.com]

On Thursday, 20 September 2018 17:44:33 UTC+1, jurb...@gmail.com wrote:
nt:

> >"electronically controlled units work much better than mechanical humidistats "
>
> Until they break. A mechanical one has a strand of soemthing in it that can be replaced, the spring can be cut down or stretched to adjust if it changes over time. The corroded wires can be replaced.

have you rebuilt a mechanical humidistat? It's nothing like as easy as a bimetal stat.

> If the chip goes bad and it has a number on it like XD333YTOT23AAA1902**/A to buy a whole new dehumidifier and throw that one in the dumpster, Freon and all.
>
> And they probably get a fucking energy star compliance certification. And your money went to a country that uses predatory trade practices. And the landfills fill up until this country is nothing but a landfill.
>
> But it's more important to hold it between 71 and 75 % because 69 and 77 % would be totally unacceptable.
>
> Right.
>
> That's not Luddite, that's green and it is actually conservative, like to conserve.

electronic RH control has more chance of surviving long term than a bit of plastic with almost no movement and almost no tension operating a switch mechanism that's barely functional because it's hopelessly weakly operated.


NT

[tabb...@gmail.com]

On Thursday, 20 September 2018 17:52:33 UTC+1, jurb...@gmail.com wrote:
nt:

unfortunately you snipped everything proceding, so who knows what we were saying. I do as a general principle agree with the use of reliable equipment where it's as cheap as junk. Only a fool wouldn't.


NT