suggestions for fixing a 16 second delay

[Gladmarr]

Hi, I'm new around here, but I'm sure glad to have found this message board.  

I have a 16 second delay - the old one - and it's got a hum.  The hum is in the dry signal only.  When you listen to just the delay line, the hum is gone.  It seems weird that the dry signal would hum, but the delay would be clean, doesn't it?  If you have any thoughts on what is causing this, please let me know.

Thanks!

:wink:

[petemoore]

SOMETHING EASY TO TRY
 FIND THE PoWER SUPPLY FILTER CAPS
 WHOOPS PROBABLY THIS HAS A DUAL POWER SUppLY SO YOULL HAVE TO FIND ....NEVERMIND
 YOU SAY OLD, THE LARGE ELECTROLYTICS ARE MoST LiKELY THE powER SupplY FIltErING CAps. eleCtrolytics dry out.
 might not be a Bad idea to change all the electro's while you're in there anyway...
 mark Polarity before removing the old capacitro with either a felt marker mark on the board, or some other reliable method...! REPLACE NEW cAPs wITh the side marked -  ..SAME WAY THE OLD ONE WAS IN THERE.
 COMPUTERS ACTIN' JEST' A 'LIL FUNNY...SORRY FOR THE CAPS

[niftydog]

Do you have an oscilloscope? Probably not, right!?! ok...

Open it up and try to find the power supply section. Use a multimeter to measure the DC voltages at the output of each power supply section.

Now, use your multimeter to read the AC voltage at those same pins. Record both the DC and AC voltages and get back to the forum. You may have a bad AC ripple in the supply.

Chances are that pete is correct; the electrolytic filter caps are buggered. But you should first try to replace ONLY the power supply caps.

[Dan N]

This site is a pretty good one on that unit:

http://www.stecrecords.com/gear/eh16/

[Gladmarr]

Wow, I didn't think I'd get that much response that fast.  Thanks all.  I do have a scope, so I can look at DC and AC signals on the power supply.  I have barely even opened this thing up.  I'm so afraid of messing up either of the obsolete parts in this puppy that I wanted to get suggestions first, then look at everything all at once for fear of hurting the guts of the pedal by opening it up too many times.  I know that sounds pretty superstitious, but hey, electronics is mostly pure freaking magic anyway.

I'll give all that a try.  I'll give you all a word when I get some idea what's up in this box.

Thanks!

[niftydog]

just look for AC ripple on the DC supply. If it's bad, you might consider changing the filter caps.