On Monday, March 20, 2017 at 1:18:00 PM UTC-4, Trevor Wilson wrote:
On 20/03/2017 11:58 AM, Phil Allison wrote:
wrote:



Not very surprisingly I cannot source a replacement BF472, so
I need to find a substitute.


I would try a MJE350(pnp/300V/500ma/20w/TO-126/hFE=30-240). Anchor
Electronics http://anchor-electronics.com/ wants US$0.95 each.


** I have already pointed out that Sydney's biggest spare parts
dealer( WES components) has the BF470 in stock for under $1.

Sylvia lives in Sydney.


**I am VERY wary about buying anything from WES now. From their ****ty
electrolytic caps (Jamicon - horrible things, one batch of 100 I
purchased had a 30% failure rate - I had to recall half a dozen units I
serviced as a precaution) to counterfeit semiconductors, I've been
caught several times. As have some of my colleagues. I readily admit
that small, cheap devices are likely to be fine though. I purchased some
large, Japanese flatpack (two screw mounting types) from WES last year.
Same type as the ones in the amp. It failed during bench testing.
Subsequent tests on replacement devices revealed a breakdown Voltage
(VCEO) of around 90 Volts. The original devices are specc'd at 230
Volts. I ended up using single screw mounted devices (same ratings),
obtained from an accredited supplier. No problems. A mate did battle
with a TV set flyback MOSFET a few years back. After many hours chasing
his tail, I suggested he stop buying WES supplied parts and go to
Element14 for the MOSFET (less than $5.00). Problem solved. WES were
kind enough to refund his money for the dodgy MOSFETs, but not the
considerable amount of wasted time.

Never again. All my electros are sourced from Element14 or RS
Components. Panasonic is my favourite brand. Phenomenally low failure
rate and well priced. That free delivery from RS is very nice. My spend
with WES has fallen dramatically.


--
Trevor Wilson
www.rageaudio.com.au

I learned the hard way about counterfeit semis decades ago. Home stereo amps that would blow up in a week after repair, horiz/HV output transistors shorting on power up, hybrid smps ICs that just didn't work or would cause severe oscillation, vertical output ICs running hot and failing in days, PTV convergence hybrid modules that defied alignment...

Here in the U.S., the only suppliers I trust are DigiKey, Mouser, and B&D Enterprises. I'm sometimes forced to buy parts through AliExpress. These are carefully tested. If one is bad, the batch gets scrapped.