Starting today the restoration of a Murphy B485 transistor radio receiver. This is a beautifully over engineered set as you'd expect from Murphy and when working I'm expecting excellent results.
Circuit features are separate mixer and oscillator transistors, early production sets employed Ediswan PXA102 transistors and later sets "intermediate stage production" employed a Mullard AF117 for the mixer and the set we're discussing has that transistor. All the other transistors are of Ediswan manufacture.
The output transistors are PXC131 operating in a split supply arrangement which was common in fifties and early sixties radios. Two 6volt Ever-Ready batteries were used, no longer available so the set will be modified for eight round cells.
Later sets made in 1961 employed Mullard transistors. Didn't Ediswan stop making transistors that year?
Till Eulenspiegel.
Would those batteries have been PP6, or maybe PP7? - I seem to recall that one of them was 6V.
Hi Marion, I'm sure those are 9 volt batteries. I think the answer is to use four battery holders which carry two C cells.
Till Eulenspiegel.
I think you're right..... It's PP1 and PP8 that were 6V. A pity the radio doesn't use PJ996 (6V lantern battery), like my Decca TP22. The Decca uses a split battery power supply too.
The Murphy B485 has the option of an external B1 Loudspeaker Baffle unit which contains the PP8 battery.
According to the service data the consumption is 17mA at normal listening levels, C cells can handle that current and give a long life. Might even get away with AA cells.
Till Eulenspiegel
Later sets made in 1961 employed Mullard transistors. Didn't Ediswan stop making transistors that year?
I've certainly seen Mazda-badged transistors (but using Pro-Electron codes) in Thorn equipment made in the late 60s, such as record players; I remember this because they were so noisy they sounded like an off-tune FM radio and I ended up redesigning the circuit to accept a BC559 in place of the (I think) AC156 as fitted.
Some information about Thorn semiconductors, the Mazda book is from 1966 so it appears that they didn’t progress to silicon types.
Around this time Thorn must have been deeply involved with Texas semiconductors and probably started to use their silicon. The 2000 CTV used Texas semiconductors.
http://wylie.org.uk/technology/semics/ThornAEI/ThornAEI.htm
Frank
Yes I recall buying Ediswan transistors in the early 60's from a Disposals store. Yes they were cheap. Yes they were noisy!
The crazy thing in those days is we had so many companies in Australia making transistors. At least 7 that I can think of.
Another Murphy transistor radio, the model B493. Like the set under discussion the mixer transistor is a Mullard AF117, all the others are Ediswan types.
One of the last "real" Murphy models, released January 1962.
Till Eulenspiegel.
Hi Frank, around 1960 nearly all the manufactures made an all transistor table radio set. The ones that easily come to mind are the models made by Bush and Ever-Ready. When fitted in the B1 baffle unit the Murphy B485 could have been used as a domestic radio set. The PP8 batteries would have a long service life.
Till Eulenspiegel.
At the end of the 60’s setting up home I was given a Tesla transistor table radio, made in East Europe earlier in the decade. It needed fixing of course but a couple of transistors and it was working, MW/LW only and either C or D cells which lasted well. The set gave us many years of service.
Frank
The output transistors are PXC131 operating in a split supply arrangement which was common in fifties and early sixties radios. Two 6volt Ever-Ready batteries were used, no longer available so the set will be modified for eight round cells.
To replace the Ever-Ready PP1 batteries eight C cells will be used. These will be fitted into four two cell battery holders, RS Components stock number 185-4663. Two battery holders are screwed together back to back and in terms of dimensions are almost the same as the original PP1 battery.
Till Eulenspiegel.
eight C cells will be used
Can we not use the old designation, Till; eight HP11s?!
Note to younger users:
- D = HP/SP2
- C = HP/SP11
- AA = HP7
- AAA = HP16
The HP/SP codes were used by Ever Ready (note that it's two words); I think (but could be wrong) that Vidor and Exide ('Drydex') used their own designations.
Maybe I should, after all back in the seventies and early eighties I sold Ever-Ready products delivered direct to the shop. The firm had a large factory complex in County Durham.
Was occasionally asked for batteries for valve portable radios.
But we can't get away from the fact the cells are now widely known as AA, C and D.
Till Eulenspiegel.
You had the Ever Ready man and van as well.
We had to stop using Ever Ready HP7 (AA) types, we had radios being returned for leaks out of the cabinet but the radio was still working fine. The Batteries were leaking but still had plenty power in them to work the radio. Not an isolated incident.
Obviously manufacturers fault, the cases were eaten through, whether too thin zinc cases or the electrolyte was wrong I don’t know.
A good article about the fall of Ever Ready, probably other good articles available, this was the first I found.
Frank
We had to stop using Ever Ready HP7 (AA) types, we had radios being returned for leaks out of the cabinet but the radio was still working fine. The Batteries were leaking but still had plenty power in them to work the radio. Not an isolated incident.
Obviously manufacturers fault, the cases were eaten through, whether too thin zinc cases or the electrolyte was wrong I don’t know.
Hi Frank, I remember that problem with the HP7 cells. HP7 wasn't the original name for the cell, was it the U11?
From Wikipedia: https://en.m.wikipedia.org/wiki/List_of_battery_sizes
Found this in a topic about batteries in a topic about batteries:
https://vintage-radio.net/forum/showthread.php?t=137633
The Wiki link was introduced by your good self.
Till Eulenspiegel.
eight C cells will be used
Can we not use the old designation, Till; eight HP11s?!
Note to younger users:
- D = HP/SP2
- C = HP/SP11
- AA = HP7
- AAA = HP16
The HP/SP codes were used by Ever Ready (note that it's two words); I think (but could be wrong) that Vidor and Exide ('Drydex') used their own designations.
Or even the old "U" designations? I remember almost everything running on "U2" an "U11" or "PP3" and "PP9", though there was the inevitable "Penlight" battery for those who owned a Penlight. "SP" as I recall, replaced "U" and "HP" was just a longer lasting version of "SP" - In modern parlance "Greater energy density". There were of course the less common battery/cells, so not forgetting the more specialised hand lamp, lantern, and 1.5v/90v radio batteries.
Just thinking about it, a modern "Energizer AA Max Plus" has a far greater energy density today, then even the best "HP2" of 1967(ish).
