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

[Hans-Peter]

I have a 97 for repair, which at first glance had no signs of error (except Reader and Printer). When I opened I was greeted with plastic splinters.
Diagnostic SD-15B ended with code 45.00
The resistor R4 I could simply replace, over a replacement for the PNP transistor Q1 1853-0395 I found nothing. So I took the universe type 2N3906. Now the Diagnostic also runs through and brings the value 10000000.00.
   
Now is the question of the perpetrator? Are there other victims?

Hans-Peter

[striegel]

(12-02-2016 09:52 PM)Hans-Peter Wrote:  I have a 97 for repair, which at first glance had no signs of error (except Reader and Printer). When I opened I was greeted with plastic splinters.
...

Wow! From the image, it looks more like direct physical impact(s) rather than heat from device failure. I don't see signs of melting, charring, or lifted traces on the circuit board beneath the parts.

Alan

[Harald]

(12-03-2016 04:07 PM)striegel Wrote:  

(12-02-2016 09:52 PM)Hans-Peter Wrote:  I have a 97 for repair, which at first glance had no signs of error (except Reader and Printer). When I opened I was greeted with plastic splinters.
...

Wow! From the image, it looks more like direct physical impact(s) rather than heat from device failure. I don't see signs of melting, charring, or lifted traces on the circuit board beneath the parts.

Alan

I agree, looks like mechanical damage to the parts.

[HP-Collection]

I guess it was a virus or a trojaner - there is not enough space for a mouse.

[Geoff Quickfall]

That's not mechanical (kinetic) damage. Looks more like a over current fracture damage. Reminds me of my grundig 4035 restoration. Two obvious damaged resistors in series on the same circuit. Tracing from the power supply to the resistors resulted in an higher current through the circuit then designed causing both resistors to fracture then fail.

Highly doubt that it was a physical impact as the board would have also shown indication no of trauma.

Grundig restored:


Before:



After:

[Harald]

Wow Geoff!

Is there anything you DON'T restore?!?
I have Blaupunkt Milano that is waiting for restoration. How did you treat the wood to get it that great looking? How did you get on with the valve technology?
My Milano only works on FM and I haven't mamaged to work out why. It has become a bit pointless by now though. MW is more or less dead in Germany now, on LW you get a few french and british stations, maybe SW migt still be interesting.

Back on topic: I would still expect to see signs of (over)heating on the resistor if the damage was done by overcurrent. Slight over currents usually result in high temperature of the whole component and the sureounding area, cracked parts usually are the result of massive overcurrents and overvoltages. In that case you would eypect to see signs of excessive heat and even arcing. The energy do burst the component has to come from somewhere.

[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

[vk6ti]

I have seen and repaired this type combo heaps of times, but usually in power supplies, mostly where someone has put incorrect power etc, or component failure.
However I would have thought just using the units batteries would not have caused that catastrophic result. ( I am not an expert in repairing calculators )
Thinking mechanical intervention would be unlikely, it is quite puzzling,
hope you get to the bottom of it.
Is the 97 a new acquisition, or did it happen while you owned it ??

Good luck with it

Ray

Geoff,
I bet that Gundig sounds good, terrible to work on, but a marvel of 60's German engineering

[Geoff Quickfall]

Hi Ray, the radio sounds incredible.

How about the power supply set incorrectly. Some HP power supplies have the 110/220 switch. And you are correct, I have seen quite a few over voltage/current damage without heat evidence.

Geoff

[teenix]

It looks like mechanical damage to me.

The resistor coil doesn't look burnt, just torn away from the central core.

There is also a scuff mark on the bend the left resistor wire.

Perhaps the PCB it was dropped or something dropped onto the PCB.

Possibly a repair job was attempted as there seems to be excess solder flux residue on the connectors below the resistor.

cheers

Tony

[Dieter]

(12-04-2016 10:54 PM)vk6ti Wrote:  I bet that Gundig sounds good, terrible to work on, but a marvel of 60's German engineering

Err... that's a whole decade earlier (1954). ;-)
German audio engineering of the Sixties was a completely different story.
For a first impression take a look at some pictures of the Braun Studio 1000 series.

Dieter

[vk6ti]

(12-05-2016 06:34 PM)Dieter Wrote:  

(12-04-2016 10:54 PM)vk6ti Wrote:  I bet that Gundig sounds good, terrible to work on, but a marvel of 60's German engineering

Err... that's a whole decade earlier (1954). ;-)
German audio engineering of the Sixties was a completely different story.
For a first impression take a look at some pictures of the Braun Studio 1000 series.

Dieter

Hi Dieter,
Yes you are correct 1954/55, I made a simple amateur mistake :-)
I have worked on tube radios and gear for about 30 years, however I don't recall
ever working on a Grundig 4035.

I see what you mean about the Braun Studio 1000, very futuristic for it's time,
there is some interesting gear floating around late 50's early 60's, especially the
transistor / tube hybrids.

Ray