Hartman Analog Flanger burnt 10ohm resistor

[BDuguay]

Hey All
A fellow has asked me to look at his Hartman Analog Flanger he bought that arrived intermittently working...sort of. He said, and I verified, there was no signal when engaged though the status light came on. The pedal uses a 3PDT switch wired for true bypass and stays light.
Upon inspection I saw a burnt resistor which matches a schematic I found here for an EH Electric Mistress as 10ohms. It's in the power section.
I replaced it with a new one and everything works now but the resistor get's very hot to the touch. I measured it at close to 60 degrees Celsius.
It looks as though its purpose is to dump 9vdc down to 7vdc for the 4049 chip.
The neighbouring 220mf and 100mf electrolytics get up to 45 degrees each.
Can anyone more familiar tell me if this is normal?
Thanks!
B.

[anotherjim]

The caps getting hot is worrying.
They could be seriously leaky and that is what's putting excessive current thru the 10R.
Then again, if the 10R is hot enough simply because of the normal circuit current and the caps are too close, then that heating can damage the caps, which in turn can cause more heating in a viscous circle. I've seen too many things with electro caps next to something that gets hot - early switching power supplies did it a lot.

I would change the caps too.

I've not seen this particular scheme, but I'm guessing the 4049 is clocking a bbd chip? I'm not sure if they pull excessive current used in that way.

[BDuguay]

I'm curious though, would leaky caps introduce noise? This unit works fine and seems fairly quiet.
B.

[J0K3RX]

Those run at 9v to 12v DC from what I have seen. Which is this one using?

[BDuguay]

I'm powering this one with a regulated 9vdc adaptor.

[anotherjim]

Your power supply is probably doing a good job of removing supply ripple itself. Also there ought to be some ceramic caps close to noisy chips and they are very robust. And, if the audio paths are based on op-amps, they do a very good job of rejecting supply ripple.
The root cause of the fault could be due to an unsuitable or bad power supply having been used. If you can see any protection diodes on the DC input, they need checking. In particular there may be a backward diode across the DC input, and if this was after the 10R, then a wrong polarity (or AC!) power supply would cook things good until the diode blows open and then the electro caps get reverse damage.
If there isn't one already, do the owner a favour by fitting a medium power schottky diode in series with the + input immediately after the DC jack.

[PRR]

> 10 ohms. ... to dump 9vdc down to 7vdc

9V-7V= 2V. 2V in 10 Ohms is 0.2 Amps. 2V times 0.2A is 0.4 Watts.

A half-Watt resistor will get HOT, and won't live forever. 

The Zener should also be hot.

Near-by caps etc will heat-up through heat conducted through the board. A test would be to mount the 10 Ohms off-board (several inch wires), probably Zener also, and see if the caps still get hot.

> for the 4049 chip.

No way a '4049 needs anything like 0.2 Amps. Are you sure of your diagnosis?

[BDuguay]

I'm not sure at all of my diagnosis now....
B.

[BDuguay]

I replaced the 1N5243 Zener and all is good. Thanks to all who contributed to the ultimate successful fix!
B.