PT Laney HC50R

[gbono]

Laney HC50 that had a history of cutting out. The issue turned out to be the PT. With the PT on the bench (secondary disconnected from PCB) and the primary connected to a VARIAC there is no secondary voltage present at any primary voltage applied. Primary windings also measure open with DVM.

The transformer in the amp has markings that identify the secondary as 2 x 21VAC (120VAC primary) - the schematic for the amp is attached for reference.

Looking for a low cost PT for this repair - found this http://www.antekinc.com/content/AN-1222.pdf but I'm wondering if it is too low of a VA rating?

[Enzo]

Probably fine.

[gbono]

Found this too looks like it has some shielding between the pri/sec - not sure what the purple wire is on the primary - shield connection?

http://www.antekinc.com/content/AS-1220.pdf

[J M Fahey]

Well they say so themselves
Just ground the purple wire, but first doublecheck it has no continuity against *any* other wire.
Voltage and VA is fine, as Enzo said.

[smackoj]

Just a comment about finding suitable replacement PTs. I have had a string of amps on my bench lately that had Pt problems and needed to be replaced. Do to the high, and going higher, cost of new transformers and my skepticism about important parts that say 'made in china' I was on the lookout for a sensible solution. I sort of stumbled onto a supply of low cost PTs when I bought a couple used, powered sub woofers at local re-sale shops. Almost always what is commonly referred to as the 'plate' amp, is non-functioning. But about 80 percent of the time the power transformer is still good. So, even though most of the sub woofer is basically junk, for the grand sum of around 5-10 dollars I end up with a tried and tested power transformer to use for other repairs. One note; buying the bigger, name brand subs is the only way to be fairly confident that the PT will be powerful and strong enough to substitute in amps like a 50 watt Laney SS amp. Here are some names of sub woofers that use better parts and are rated at higher watts: Boston Acoustics, Bose, Klipsch, JBL, Acoustic Research, BandW, Denon and Polk Audio just to name a few.