HP97: Who was the killer (resistor or transistor)?

[Geoff Quickfall]

Harald.

I too, would expect more heat signature, but I have seen these literally explode leaving no charring or heat related damage. Especially the transistor.

That doesn't rule out the mechanical damage. Just an idea (concerned about an existing electrical fault) but obviously reading the original post again, nothing was done to the power supply and the resistor/transistor were replaced and have not failed. So mechanical it is.

Hans.

The next numerical error message is shown, don't have my HP97 document available, have you deciphered it? Is it in series with the resistor and transistor, or not associated to that circuit? If mechanical damage is suspect then check all solder joints near the damage. Remelt them to be sure a cold solder joint does not exist.

Radio.

:-)

Lots of FM and MW (am) here. FM is packed and difficult to find a free frequency. I pump my iPad music playlist through the phono amplifier jack modified to accept a stereo 1.5 mm jack. The radio then amplifies the sound and feeds it through two matching (1953) post modern grundig speakers also restored. The valves distort the sound into the warm pleasant range. We no longer use the techniques sound system.

Valves were easy to source, the electronics visible and organized (German not American). Got a couple of spare magic eyes just in case. The FM only goes to 101 MHz bcause the 101 - 108 valve had not been created at the time of this model radios production date.

The case was stripped, sanded, stained and then varnished. 20 coats of varnish but the weT/dry (400, 800, 1200, 2000 grit in that order) fine sanding started at coat 8 until coat 20. Used decomposed limestone (5000 grit) for the final hand rub followed by beeswax polish.

The gold/brass trim is the FM antenna!

Geoff