Germanium Hi-Fi amp ??

[Phil Allison]

** 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/large/259809-nikko_fam12_tuner_nikko_trm40_amplifier.jpg

Insides:

http://www.zmdz.com/bbs/incomefiles/201211/2418521149767.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

[Trevor Wilson]

**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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[Eiron]

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.

[Graeme Wall]

:-)

--
Graeme Wall
This account not read.

[Phil Allison]

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

[Dave Plowman (News)]

In article <78ca3a0f-e721-4429...@googlegroups.com>,

Phil Allison <palli...@gmail.com> 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 da...@davenoise.co.uk London SW
To e-mail, change noise into sound.

[Don Pearce]

On Fri, 10 Jun 2016 14:50:08 +0100, "Dave Plowman (News)"
<da...@davenoise.co.uk> wrote:

>In article <78ca3a0f-e721-4429...@googlegroups.com>,
> Phil Allison <palli...@gmail.com> 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

[Trevor Wilson]

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.

[Phil Allison]

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/attachment.php?s=1c431678cac315bf62baff06318ee206&attachmentid=75254&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

[Brian Gaff]

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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[Brian Gaff]

Funnily enough I used to have an obscure data book on olddevices which I
gave to aan old chap some time ago. One item I recall was a silicon
replacement for germanium transistors. I thought this was impossible due to
the difference in their voltage drop, but apparently they worked well enough
at the time.

I think it was mainly for the AC series of transistors.

Brian

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"Trevor Wilson" <tre...@SPAMBLOCKrageaudio.com.au> wrote in message
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[Brian Gaff]

Thermal runaway. Remember that well. R&TV Supplies in Acton did a transistor
radio kit called the elegant 7, yes a whole 7 transistors.
Trouble was almost evey component in it was a substtute for the intended
one in the original design. the single ended push/pull ciruit specified
Get 114 transistors, but the supplied ones on f dubious manufactur were
labelled S1. The radio worked for about ten mins, then started to distort
and stop. The S1 transistors got red hot. Leaving it off for a few minutes
repeated the effect. Probably not have got away with this on a mains psu.
After some poking at the company they sent us the right ones and then it
worked and still did the last time I tried it.
Goes to show tht thermal runaway can be very interesting.
No heat sink in this radio as it had a 35 ohm speaker and only gave out 500
Mw supposedly.

Brian

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"Don Pearce" <sp...@spam.com> wrote in message
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[Eiron]

On 11/06/2016 08:43, Brian Gaff wrote:

> 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.

This one? http://rk.nvg.ntnu.no/sinclair/audio/z12.htm
What a pile of crap!

I became quite adept at fixing Z30s in my youth.
http://rk.nvg.ntnu.no/sinclair/audio/z30.htm
Maybe a much bigger heat sink would have helped
but they hardly ever survived a party.

--
Eiron.

[Brian Gaff]

Chuckle well a lot of the problem with Sinclair was that his designs fine
but when they made them they stopped at nothing to source the cheapest bits
they could to the detriment of the actual performance.
The IC amps were even worse. The IC10, was basically a power op amp with no
protection against self destruction.
The IC12, was I believe a Texas Instruments design, again with no
protection and far too much gain close to the high power parts which meant
that any supply issues were fed back to the input making it sound very bad.

The only bit of his bolt together hi fi that did work quite well was the
stereo decoder for the fm crap tuner.
I did put that on aan old tuner I had after removing the de emphasis and it
sounded very nice and low his levels, but then there was not much inside it
an a single chip was there?

Brian

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"Eiron" <Evelyn....@live.com> wrote in message
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[Dave Plowman (News)]

In article <njjemf$5gl$1...@dont-email.me>,

Brian Gaff <bri...@blueyonder.co.uk> wrote:
> Chuckle well a lot of the problem with Sinclair was that his designs
> fine but when they made them they stopped at nothing to source the
> cheapest bits they could to the detriment of the actual performance.

Remember one of his pre-amps where all the pots were open frame pre-sets
with spindles attached. Not exactly built to last.

--
*Never test the depth of the water with both feet.*

[tony sayer]

In article <ds22fc...@mid.individual.net>, Eiron
<Evelyn....@live.com> scribeth thus

From that first site......


Like many Sinclair products in the early 1960s, the Slimline relied on
the use of metal-alloy transistors rejected by Plessey for their
original purpose in early transistorized computers. However, they were
good enough for Sinclair's relatively undemanding purposes and were
either incorporated in the kits or sold as separate transistors for a
reported profit of up to 700 per cent. Sinclair's then wife, Ann, was
pressed into service to sort and test them:

"The transistors used to arrive in sacks. About three or four sacks
would arrive, about the size of a sack of potatoes. I had test equipment
consisting of a box that gave a different pitched buzz according to the
transistor, and I must have tested a million of them altogether. It
really became monotonous, because I"d no sooner finished one sack than
another would turn up."

Sinclair was certainly an early convert to industrial recycling, as one
incident shows. Texas Instruments at Bedford used a large batch of
reject transistors as hardcore for a driveway. Sinclair found out about
this, presumably through industry contacts, and rather than shrugging
his shoulders at a missed opportunity negotiated a price for digging the
whole lot up again!

--
Tony Sayer

[Brian-Gaff]

Yes and his slide tuner scale was basically the same issue only in a slider
not a rotating pot.
If you replaced that with a multiturn as i did once to see if it worked, it
was miles better, but still picked up aircraft.
Brian

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"Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
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[Brian-Gaff]

Sounds about right. I assume you knew about the dodgy ram chips in the
Spectrum which had half the chip duff, and a link in the pcb to select the
working half only in each case.

Brian

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"tony sayer" <to...@bancom.co.uk> wrote in message
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[Eiron]

On 12/06/2016 12:45, Dave Plowman (News) wrote:
> In article <njjemf$5gl$1...@dont-email.me>,
> Brian Gaff <bri...@blueyonder.co.uk> wrote:
>> Chuckle well a lot of the problem with Sinclair was that his designs
>> fine but when they made them they stopped at nothing to source the
>> cheapest bits they could to the detriment of the actual performance.
>
> Remember one of his pre-amps where all the pots were open frame pre-sets
> with spindles attached. Not exactly built to last.

Linear pots for the volume control!

--
Eiron.

[Phil Allison]

Eiron wrote:

>
> I became quite adept at fixing Z30s in my youth.
> http://rk.nvg.ntnu.no/sinclair/audio/z30.htm
> Maybe a much bigger heat sink would have helped
> but they hardly ever survived a party.
>

** Someone gave me one Z30 module and a "Project 60" manual in the early 70s - it all sat in a drawer for several years until I figured out a use. In the manual was a schem for making the Z30 into a power sine wave oscillator using a Wein bridge circuit. See figure 4.16.1.a

http://www.epanorama.net/sff/Audio/Circuits/Power_amplifiers-linear/Sinclair%20Project%2060.pdf

I quickly lashed up one built to oscillate at 67Hz, with a few Hz range of adjustment. Used with an unregulated 30V supply, it ran nicely with the output feeding the 8ohm winding of a 15W UL output tranny from an old valve amplifier.

The primary was used to drive a small synchronous motor with a 240V pure sine wave. The finished version had a toggle switch to bring the frequency down to a nominal 50Hz.

This is a pretty tough job for a puny Sinclair Z30 module, but it never failed in over 20 years of use.

Who can guess what it did ?


.... Phil

[Brian Gaff]

Sounds like a turntable speed control device, when you said did for, did you
mean that literally, ie killed?

Brian

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[Phil Allison]

Brian Gaff wrote:
>
>
> Sounds like a turntable speed control device,
>
>

** Correct.

Was used it to drive the 16 pole, synchronous motor of a JH Turntable.

Made in Melbourne by "JH Reproducers" the TT used a soft belt wrapped around a lightweight, 30cm dia aluminium platter driven by a almost vibrationless motor with a two step pulley. The steps enabled 45rpm and 33.3rpm discs to be played.

It was far more convenient to have electronic control and the ability to trim the speed as JHs usually ran a few percent fast - allegedly to compensate for the drag effect of a "dust bug".

I know such a combination sounds unpromising, but when mounted on an inch thick acrylic base and supported on three beehive springs - it became a genuine Linn Sondek killer.

I used mine with a uni-pivot tone arm and Shure V15 mkIII up to and well beyond the arrival of CDs.

> when you said did for, did you
> mean that literally, ie killed?
>
>

** No, I gave the set up away to a friend, along with all my LPs, when they had been long out of use.



... Phil

[Brian Gaff]

I still have an old Technics SL5 with an Ortofon cart which still goes, but
is begining to make noises in the parrarell arm mechanics due to the grease
drying out.

I use it cos it needs no sight.

Brian

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