LH500 tube replacement

RatzaChewy · #1 10-28-2010, 09:06 AM

Bought a NOS Philips 5751 as I thought the amp was breaking up just a little too much past 6 with he stock EHX valve. But there's one problem, there's a valve shield that I can't remove for the life of me. The top part comes off fine, but there's a bottom half that's attached that prevents removal of the valve which is attached to the circuit board but isn't held by a screw. Haven't managed to find a thing on the net, so any help would be appreciated.

BassmanPaul · #2 10-28-2010, 09:57 AM

That sounds like the tube base in which case the tube just pulls out. Can you post a photo?

RatzaChewy · #3 10-28-2010, 04:13 PM

Quote:

Originally Posted by BassmanPaul

That sounds like the tube base in which case the tube just pulls out. Can you post a photo?

Afraid not for now, all I have is my phone and it's only good under natural lighting.

BassmanPaul · #4 10-28-2010, 04:22 PM

Quote:

Originally Posted by RatzaChewy

Afraid not for now, all I have is my phone and it's only good under natural lighting.

Then take your amp outside!

Washishimi · #5 10-28-2010, 04:44 PM

If I remember correctly, when I swapped the tube out of my LH1000, once I twisted off the top piece that has the spring in it that holds down the tube, the tube pulled right out. Here is a pic of the internals from another thread showing the tube without the spring holder on top (at this point in the picture, the tube should pull straight out):

BassmanPaul · #6 10-28-2010, 07:32 PM

That's exactly what I was visualizing.

.

timmus · #7 10-28-2010, 07:39 PM

sometimes the bottom half will grip the tube envelope due to size differences in the OD of the tube glass...gently "rolling" the tube top a bit in a circlular motion as you pull up will usually persuade it to come out...don'tget too aggressive as you may crack the socket and/or seals where the pins go through the glass.

Larry Hartke · #8 10-28-2010, 10:25 PM

Ratzachewy...I've got your back, if you aren't sure about getting the tube out call me and I'll help you. Not to worry, it's me here!

Larry 201-680-8153 Cell

RatzaChewy · #9 10-29-2010, 05:45 AM

Success

The EHX is quite a wide valve and it seems to be what caused the 'problem', even though it was mostly just me being far too hesitant to apply much force at all. Pulled it out with ease eventually. Shame my replaced tube took a small fall off the table, the sound quality and noise floor is great, but I had a tiny problem with feedback, luckily, this was seriously reduced once I put the casing back on, so I doubt it'll be a problem.