Eddystone 830/7
Welcome to the Eddystone 830 page. I got this nice receiver as a
Christmas gift and was my first tubed Eddystone. Here you have my comments about its restoration
and different problems I found while restoring it. Note that REMARKS are written
later and reflect current information or comments. I will add more information when I do the
alignment. If you want to contribute anything, please, feel free to
send me a message. Thanks!
REMARK: here you have some pictures of the set as I got it. As you can see, there
was plenty of dirt... compare with pictures once it was cleaned, later in this document!
So I took it home... to find somebody had badly butchered it :-(.
It seems power transformer 6.3VAC winding was shot, so there were some
wiring mods, not neatly done, to take filament power form two 3.15V
outputs in the transformer (REMARK: later I discovered that this is the
usual way 830s are wired and that there are two secondary windings in
the power transformer which are not used, for 5 and 6.3VAC. But, anyway,
what was true is that the filament wiring was changed, as it consists
in two different 6.3 VAC windings and one of them was now not connected).
Then, in most of the tubes, it was evident (poor soldering job) a wiring
change. And that included some added components. Also, the noise
limiter / AGC switch wafer was just missing, and some of its wires poorly
soldered and the others just cut. Power cord was also replaced in a loosely
way. There were also some missing covers. All in all, 'just a pretty face' :-(
I have the chance to pick up the other 830 in the pile... I know it is
cosmetically worse (at least front panel wise). And it is probably an 830/2
(REMARK: it was really an 830/5, which is very close to the 830/7, but
it was really in far worse shape) (it has an slightly different color scheme).
But if it is in better condition internally, I will take it, as fixing the other
one seems as a big challenge and some things just could not be fixed reasonably
(as some charred wires, due to the lousy soldering job). I will let you know what I
find. In case the other 830 is also in bad shape, I will go for the Electra.
Well, sometimes things are not as nice as they look at first glance. But,
anyway, I am lucky to be able to select which receiver I want, checking it
at home and then deciding. Imagine if you buy a rig overseas and, once you
get it, you discover it is as the 830/7 I got...
BTW, in the pile (NOT available for me to have) there are some other
interesting receivers, as a Marconi Nebula (about a 9 cosmetically) and
Apollo (about an 8). Also an ITT-Mackay 3010C (in great shape). And older
Eddystones, a Redifon R-50M, ... I can take any of them home and use it for
some days if I wish... Perhaps some day, once I get my 'gift' receiver.
REMARK: as you can see, first impression I got from the 830/7 was really bad.
But I am not easy to convince a set is not worth the time to fix it... so I
finally decided to keep it and try to get it back to life!
But now the switch is rewired as it should and, once there, I
replaced some charred wires (which were burnt when the rewiring was done)
and routed conveniently some other missplaced wires. Another missing thing
was the ANL/AVC switch wafer, which I replaced.
And then I look at the poor
job done to rewire the filament power wiring. I changed some wires,
re-routed some others and added fasteners so the wiring looks good,
although it is not original.
Then I took out all the valves (remember, this is a british set ;-) ) and
checked them in my TV-7C/U. All except RF amplifier (V1) showed good
readings, so I replaced V1 and connected the set. After a while I got some
random 'cracking' noise from the speaker, no received nor calibrator
signals. But tapping in some chassis parts I got a loud 'pop' at the
speaker. So I started to look for loose contacts or bad soldering joints,
armed with a plastic stick. I discovered a couple of 'obvious' faults: a
coax shield which shorted another connection in a wafer switch and a
resistor which had never been soldered; it was just touching at one end!.
This set was manufactured around 1969, so it had been that way for no less
than 32 years... Fixing both things removed the loud 'pop' when tapping the
set, but the random noise continued same way. I suspected of a 0A2 voltage
regulator (it uses two), as the noise was the same with the AF gain at
minimum, but replacing them did not fix it. It was too late (00:30) so I
let it for next day.
I will continue troubleshooting the set, from the speaker to the IF and RF
sections, injecting signals, until I locate the (first) faulty stage. BTW,
AF amplifier seems to work fine, as it produces the usual buzzing when
touched with a screwdriver. But there is an obvious fault, as the S-meter
is almost fixed in the upper part of the scale and RF/IF gain just barely
move it.
I had checked output stage with a signal generator and it worked fine. But
previous stage, a 100kHz IF strip, was just not working. It is a two 6BA6
tube stage and injecting signal in the grid of any of them generated no
output on their respective plates... so something was wrong. I checked same
way the IF transformers to find they were fine. So I measured voltages at
different tube pins to find that cathode voltage was, by far, too high
(around 160VDC)...
What did I to get the rig working?. Well, thanks to Dave MW1DUJ, who sent
me an scanned copy of the schematics, I found that the set has a MUTE
condition which should be disabled by shorting two pins in a multiple
connector on the rear of the set. It is same connector used for the speaker
/ line outputs. Of course, I did not get such connector with the set so I
had temporarily connected the speaker directly by means of a coax cable to
the back (internal side) of the connector, at its 3.2 Ohm position. But had
no clue there was a MUTE which needed to be disabled :-)!
Once I got the receiver working, I dealt with the 'cracking noise'. Some of
you suggested a bad capacitor to be the culprit of the noise. As the noise
was the same at all AF gain settings, I began troubleshooting with my
trusty Tektronix 475 oscilloscope, from the output tube to previous stages.
Of course, the crackings could be seen at the plate of the 6AQ5 output
tube. But they were also at the input grid. So they were also at the 6AT6
detector tube plate but not at any of its input pins. So something was not
right at the 6AT6 plate circuit!. There were just three 'suspect'
components: a coupling cap, a bypass cap and a resistor (connected to B+).
I disconnected the bypass cap and the noise was still there. Then I lifted
the coupling cap (which went to the 6AQ5 input grid) and the noise was not
gone. So there was just one component which could be the culprit, a 270k
Ohm resistor to B+!. I lifted one leg and it read open circuit with my
Fluke 77... suspecting!. So I put another 270k resistor and connected the
receiver... and the cracking noise was gone. Hooray!!!. As the old 270k
resistor was still coneected at one side, I put the DVM on its lifted leg
to read a non-stable voltage, from about 1 to 4 VDC... the cracking noise,
for sure.
So this is the current status of the Eddystone 830/7 project. Now I just
need to carefully clean it and, once I get a manual, check its alignment.
So far I have found that all the works I had previously done (rewiring a
butchered band switch wafer, replacing the AGC/NL wafer, resoldering loose
connections, rewiring filament power cabling, replacing a weak RF amplifier
tube, ...) were fine and everything is now working as expected. By the way,
the butchered band switch wafer, in its standard condition, just bypass the
'band spread' function in lower three bands. I have found that it works
fine as it should, bypassing it, as the dial has enough size to deal with
lower bands without band spread. And, anyway, this is the original
condition of the set, as it should be ;-)
I will probably do some extra work to let the filament wiring as it was
originally. There is one tube, the VFO, which uses a completely different
filament wiring, directly form the main transformer. All the other tubes
share another filament wiring. I don't know why, somebody changed this and
put the VFO tube filament in parallel with all the other tubes...
Cosmetic works on the receiver:
Here you have some pictures of the current looking of the receiver:
Eddystone 830/7 Repair Notes
3/1/2001
Yesterday I picked up an 830. I have good and not so good news.
I found it was an 830/7 model and front panel was about an 8. Nice!. Eddystone 830/7 as received
Mc dial detail
kc dial detail
5/1/2001
Yesterday I had some time to work on my 830/7 project. I removed most parts
of the mixer assembly (difficult task, as it is enclosed in a die cast
aluminum chassis, with very limited access to some parts), as it had been
rewired and I wanted to restore original circuit. It seems that a wire got
loosen from a difficult to access wafer connection, and somebody decided it
was better to rewire than disassemble. I understand why, as it took lots of
hours!. bottom view; rewired part circled
band switch rewired wafer
dismantled band switch
missing ANL/AVC switch wafer
5/1/2001
Well, I am not yet finished with the receiver (it still needs some
cleaning, specially on its dial, front panel and knobs and perhaps an
alignment), but I have got the receiver working in all its nine bands. And,
by the way, it seems pretty stable and sounds really fine :-)!
Now some pictures! main dial and knobs removed
kc dial mechanism
front panel (left)
front panel (right)
Eddystone 830/7
S-meter detail
kc dial detail
kc dial detail
Mc dial detail
By now, this is the end of the story... I will add more information if I work more on the rig. Thanks
for reading!
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