Jump to content

How much voltage in a preamp?


Coytee

Recommended Posts

Ok, so I have a Peach preamp.  I think it is the first version (if that matters)

 

The pots can use a shot of Deoxit which happened to arrive over the last couple days.

 

Preamp is out of system and easily accessible to take apart and have at the pots.

 

I'm just wondering if there is any stored electricity in something like this that warrants the same caution as a power amp?

 

This is a schematic of the Peach II which I'd presume to be 'similar' to the original.  

 

Thoughts?

 

 

PeachII_schem.gif

Link to comment
Share on other sites

Yes.  Any tube needs about 100 volts or more to operate and I'm sure these do too.  Maybe these are less but don't take a chance.  Big power tubes use several hundred volts btw.

 

I don't see any bleeder resistors on the several power cap and so they should be discharged before you put your fingers, or metal tools, in there.   Of course you should unplug the unit first.

 

 

WMcD

 

 

 

 

Link to comment
Share on other sites

It's about the combo of voltage and current, not just voltage.  A preamp compared to a power amp is a lower current device, though here we have a fairly high amount of potential current stored in the filter caps.   If I were tech-ing around inside there, I'd probably add a bleeder, but I'm not advising you do so if it is at all out of your element to sort out.  Follow the 'one-arm-behind-back' rule, and don't touch inside and outside the open unit with both hands if in doubt of what you're touching; prevents a path through the body.  I wouldn't expect any difficulty if you are just cleaning pots.  

Link to comment
Share on other sites

Reason I'm asking is I've never done a deoxit with a control...  my goal is to actually clean the pots on my three Crown amps.

 

I'm aware that I have to be careful there (and have found what appears to be their shorting process)

 

None the less, I was thinking I'd "practice" on the Peach since it needs cleaning too.

Link to comment
Share on other sites

Really, really make sure the deoxit has all evaporated before you power it back up. Has a nice Yamaha pro amp make a bunch of sparks onece... I'm surprised it didn't get some flames going.

 

Bruce

Link to comment
Share on other sites

Danger is over...  sprayed cleaner & oil (both the Deoxit stuff) in there.

 

Was hard to get into the little hole.  Someone (I think DJK) gave an interesting idea once...  take a flame & melt the tube while stretching it out to make it thinner.  Then cut it and you have a smaller exit hole.

 

Didn't do that...I smashed it with some pliers to make it flat on two sides (the holes were rectangles)

 

Letting it dry right now.  

 

My intent, if I can ever get the guts to do it....  is to offer it up for sale.

 

I know the two gains are scratchy because I kept them at 100% gain all the time and realistically, never rotated them.  (I did in an absolute sense, just not often)

When I did, I could hear the scratch going on.

 

 

Link to comment
Share on other sites

Side bar:  I ended up doing it 2-3 times as I wasn't sure how much fluid was actually getting inside.  There is some on the board....was it overspray or did it drip out?  I don't know.

 

How to be 100% sure....

 

Well....I have a diabetic cat who gets four (yes 4) shots per day...  I have a bunch of needles.  I can use one of his new needles, spray some Deoxit into the cap that covers the plunger (use it as a small cup) and draw the fluid out of there and then use the needle to pinpoint squirt the fluid directly into the opening.

 

In essence, it worked (needle was a touch short)  BUT....the plunger essentially locked up on me.  I managed to squirt some but it almost seems as though the fluid started to dissolve the plunger (it didn't but that's what it seemed like)

 

Did it for both the cleaner and the lub.  Put preamp back in wooden case and now it sits.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...