** Hi,

does anyone still use germanium transistor amps - anywhere ?

Had a late 60s "Nikko TRM40" stereo amp on the bench this week, in sad looking condition. I reckoned it been in storage for a couple of decades and was surely uneconomic to repair. There was plenty of dust inside and ALL the transistors were germanium types plus the power stages used driver transformers for the TO3 outputs, see pics of similar amp:

Front panel:

http://img.usaudiomart.com/uploads/l..._amplifier.jpg

Insides:

http://www.zmdz.com/bbs/incomefiles/...8521149767.JPG


Initially, almost nothing worked since corrosion was causing bad or no contact in all the pots, rotary and slide switches plus both loudspeaker circuit breakers. However, after some TLC and a little WD40 in the right spots, those problems disappeared and I had a working amp. Amazingly, all electros tested good on my ESR meter.

The next step was to test power output & THD at 1kHz which resulted in 10 Watts into 8ohms at about 1% for each channel. At the 1 Watt level, THD dropped to 0.35%, mainly third harmonic which agrees with the maker's specs.

However, THD increased at higher frequencies soon reaching double digits. Visible slew rate limiting on a scope began at *3kHz* becoming severe above that frequency - square wave testing showed it was a mere 0.3V/uS in the negative direction !! TIM & SID must have been well pleased.

The damping factor tested around 9 or 10 and the amp was fairly noisy on all inputs. The Nikko was affordably priced in 1968 and competed with budget valve amps with similar power ratings.

A least you never had to feed it any new valves.



..... Phil

On 10/06/2016 7:34 PM, Phil Allison wrote:

** Hi,

does anyone still use germanium transistor amps - anywhere ?

Had a late 60s "Nikko TRM40" stereo amp on the bench this week, in
sad looking condition. I reckoned it been in storage for a couple of
decades and was surely uneconomic to repair. There was plenty of dust
inside and ALL the transistors were germanium types plus the power
stages used driver transformers for the TO3 outputs, see pics of
similar amp:

Front panel:

http://img.usaudiomart.com/uploads/l..._amplifier.jpg

Insides:

http://www.zmdz.com/bbs/incomefiles/...8521149767.JPG


Initially, almost nothing worked since corrosion was causing bad or
no contact in all the pots, rotary and slide switches plus both
loudspeaker circuit breakers. However, after some TLC and a little
WD40 in the right spots, those problems disappeared and I had a
working amp. Amazingly, all electros tested good on my ESR meter.

The next step was to test power output & THD at 1kHz which resulted
in 10 Watts into 8ohms at about 1% for each channel. At the 1 Watt
level, THD dropped to 0.35%, mainly third harmonic which agrees with
the maker's specs.

However, THD increased at higher frequencies soon reaching double
digits. Visible slew rate limiting on a scope began at *3kHz*
becoming severe above that frequency - square wave testing showed it
was a mere 0.3V/uS in the negative direction !! TIM & SID must have
been well pleased.

The damping factor tested around 9 or 10 and the amp was fairly noisy
on all inputs. The Nikko was affordably priced in 1968 and competed
with budget valve amps with similar power ratings.

A least you never had to feed it any new valves.



.... Phil



**If you need germanium devices, Rockby have some interesting ones in
their specials list. Amazing those caps were all good. I just serviced a
3 year old M-DAC. I started marking the bad electros, until I realised
it would be easier to mark the good ones. I have to replace around 60
caps! In a DAC!

--
Trevor Wilson
www.rageaudio.com.au

---
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On 10/06/2016 10:48, Trevor Wilson wrote:


**If you need germanium devices, Rockby have some interesting ones in
their specials list. Amazing those caps were all good. I just serviced a
3 year old M-DAC. I started marking the bad electros, until I realised
it would be easier to mark the good ones. I have to replace around 60
caps! In a DAC!


Did you hear about the wheeltapper who condemned all the wheels one day
until he realized that his hammer was cracked?

--
Eiron.

On 10/06/2016 11:14, Eiron wrote:
On 10/06/2016 10:48, Trevor Wilson wrote:


**If you need germanium devices, Rockby have some interesting ones in
their specials list. Amazing those caps were all good. I just serviced a
3 year old M-DAC. I started marking the bad electros, until I realised
it would be easier to mark the good ones. I have to replace around 60
caps! In a DAC!


Did you hear about the wheeltapper who condemned all the wheels one day
until he realized that his hammer was cracked?


:-)

--
Graeme Wall
This account not read.

Trevor Wilson wrote:

**If you need germanium devices, Rockby have some interesting ones in
their specials list.

** I have an AD162 in my old bits box - never used a germanium type in 30 years.

Amazing those caps were all good.

** Yeah - all ELNA brand, like I used to buy from Radio Despatch in the 70s.


I just serviced a
3 year old M-DAC. I started marking the bad electros, until I realised
it would be easier to mark the good ones. I have to replace around 60
caps! In a DAC!


** SMD ones, I bet.

Too much heat during assembly allows the juice out.


..... Phil

In article ,
Phil Allison wrote:
does anyone still use germanium transistor amps - anywhere ?

Just by coincidence used one yesterday. A couple of ancient Henry's radio
kits which I put in a case with a rudimentary pre-amp many years ago. Only
10 watts per channel. The sort of thing you could leave lying around and
wouldn't get nicked. ;-)

Never did any measurements on it - but it sounded OK for the things it got
used for.

--
*You're never too old to learn something stupid.
Dave Plowman London SW
To e-mail, change noise into sound.

On Fri, 10 Jun 2016 14:50:08 +0100, "Dave Plowman (News)"
wrote:

In article ,
Phil Allison wrote:
does anyone still use germanium transistor amps - anywhere ?

Just by coincidence used one yesterday. A couple of ancient Henry's radio
kits which I put in a case with a rudimentary pre-amp many years ago. Only
10 watts per channel. The sort of thing you could leave lying around and
wouldn't get nicked. ;-)

Never did any measurements on it - but it sounded OK for the things it got
used for.

I seem to remember you had to be conservative with Germanium power
amps. Thermal runaway was always lurking just around the corner.

d

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On 10/06/2016 9:04 PM, Phil Allison wrote:
Trevor Wilson wrote:

**If you need germanium devices, Rockby have some interesting ones in
their specials list.

** I have an AD162 in my old bits box - never used a germanium type in 30 years.

**I have AD162 AND 161s in my box of bits. I needed a pair about 18
months ago. They turn up from time to time.


Amazing those caps were all good.

** Yeah - all ELNA brand, like I used to buy from Radio Despatch in the 70s.

**As a young buck, I caught the train to RDS to bus _A_ capacitor. I was
presented with an ELNA and a (larger) Ducon. I asked for the Ducon
(because it was Aussie made). The guy behind the counter just muttered:
"The bigger the cap, the bigger the bang."



I just serviced a
3 year old M-DAC. I started marking the bad electros, until I realised
it would be easier to mark the good ones. I have to replace around 60
caps! In a DAC!


** SMD ones, I bet.

**Nope. Every one was through hole. Most had bulging tops. Funnily
enough, the M-DAC also uses 20 or so OSCON caps. I pulled a handful out
and they measured fine. Better than fine, actually. Pretty lucky, since
I couldn't source more OSCONs in the values required, unless I bought
1,000 of the suckers. OSCONs not cheap. Also through hole types.


Too much heat during assembly allows the juice out.

**Yep. Seen it, but not in this case. Just crappy caps. Voltages on the
caps were well within reason.


--
Trevor Wilson
www.rageaudio.com.au

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Trevor Wilson wrote:



**I have AD162 AND 161s in my box of bits. I needed a pair about 18
months ago. They turn up from time to time.


** Right - in old Playmaster kit amps and vintage "stereograms" like this HMV:

http://www.vintage-radio.net/forum/a...4&d=1358783236



**As a young buck, I caught the train to RDS to bus _A_ capacitor. I was
presented with an ELNA and a (larger) Ducon. I asked for the Ducon
(because it was Aussie made). The guy behind the counter just muttered:
"The bigger the cap, the bigger the bang."



FYI:

ELNA now make electros specially for high end audio applications - using natural silk and hemp fibres in their construction.

http://www.elna.co.jp/en/capacitor/onkyou/silmic.html




..... Phil

I was not aware that the Japanese ever imported anything with more than a
few Germanium transistors in, say a tuner, at all.
Their main failing was that they thermally drifted and were hence hard to
control at crossover points in push pull stages. Most of the car radios of
the time seemed to use large class A power transistors and a. His was a
problem and the bigger power transistors seemed easy to destroy if fiddling
inside.

I had a Sinclair z12 amp that could put out a whole 12 watts, but although
it was not bad for crossover, it did sound kind of fluffy at times.

One of the issues with Mullard small signal transistors used in pre amps and
tuners such as OC44, OC71, OC 170 types seemed to be the degradation of the
encapsulation material over time, rendering them basically useless as the
whole thing as shorted out inside.
Talk about self destruction.

I had an Armstrong tuner that went this way, one of the 500 series.

I noticed though that them old Japans transistor radios using little square
silver transistors of the Germanium type seemed to go on for ever. Usually
capacitors or the tuning capacitor killed them not the semiconductors.

Brian

--
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Blind user, so no pictures please!
"Phil Allison" wrote in message
...

** Hi,

does anyone still use germanium transistor amps - anywhere ?

Had a late 60s "Nikko TRM40" stereo amp on the bench this week, in sad
looking condition. I reckoned it been in storage for a couple of decades and
was surely uneconomic to repair. There was plenty of dust inside and ALL the
transistors were germanium types plus the power stages used driver
transformers for the TO3 outputs, see pics of similar amp:

Front panel:

http://img.usaudiomart.com/uploads/l..._amplifier.jpg

Insides:

http://www.zmdz.com/bbs/incomefiles/...8521149767.JPG


Initially, almost nothing worked since corrosion was causing bad or no
contact in all the pots, rotary and slide switches plus both loudspeaker
circuit breakers. However, after some TLC and a little WD40 in the right
spots, those problems disappeared and I had a working amp. Amazingly, all
electros tested good on my ESR meter.

The next step was to test power output & THD at 1kHz which resulted in 10
Watts into 8ohms at about 1% for each channel. At the 1 Watt level, THD
dropped to 0.35%, mainly third harmonic which agrees with the maker's specs.

However, THD increased at higher frequencies soon reaching double digits.
Visible slew rate limiting on a scope began at *3kHz* becoming severe above
that frequency - square wave testing showed it was a mere 0.3V/uS in the
negative direction !! TIM & SID must have been well pleased.

The damping factor tested around 9 or 10 and the amp was fairly noisy on all
inputs. The Nikko was affordably priced in 1968 and competed with budget
valve amps with similar power ratings.

A least you never had to feed it any new valves.



..... Phil