Hi Garey, All,
Thank you Garey for your answer.
I did do most of the "obvious" things for the R4C like some you
mentioned, but not with a good result yet :-(
I will have to go over it once more thoroughly I guess and follow your tips
But for the moment I have put aside the R4C and am concentrating on the
AC4 refurbishment.
I want to have some status on the T4XC first, because I could not power
it up at all yet.
The AC4 PSU I bought separately was dead and a mess when I opened it.
Leaked capacitors, modifications (repairs?), bad solder joints and loose
connections.
Fortunately nothing blew up when I tried to power it up to measure its
output voltages.
(Just the AC4, with a bridge at the plug; not connected to the T4XC!)
I have cleaned out the whole inside of the unit, keeping only the
transformer, fuse holder, cinch socket, VOX connector and the cable
assembly / plug.
I first considdered buying the AC4-R refurbishing kit, but got a good
deal on some board with HV caps already fitted.
I could cut it in two (one half for the 650 Volt supply and the other
half for the 250 Volt supply) and to size and they fit nicely to the
side panels of the AC4 chassis after removing the old caps fitted to the
chassis.
.
I think I want to also modify it a little bit.
Fitting a 3 pin power socket, an extra DPDT mains switch on the unit
itself, fuses / fuse holders for all voltages, maybe a safety-relay for
enabling the 650 Volt only when bias is present, are some of the ideas.
I am waiting now for some parts that did not arrive yet so I think I'll
give the R4C another try.
As for the tubes 6JF6, I will not use them at this time, if ever.
I'll keep you posted.
73's,
Henry - PA0HJA
On 2/9/2011 6:52 PM, Garey Barrell wrote:
Henry -
The R-4C probably needs only a good cleaning/DeoxIT treatment.
Primarily the rotary switches, but also the tube and crystal sockets.
Go through with a screwdriver and check all chassis hardware, tube
sockets, PC boards, terminal strips, shields, essentially every screw
that goes into the chassis. If not tight, tighten firmly, if tight,
loosen slightly and retighten. This should take care of most problems
that occur in long term storage.
Follow the same process in the T-4XC, then troubleshoot what remains,
if anything!
I believe the screws in the bottom of the AC-4 are 6-32 x 1/4" pan head.
The 6JF6 is a 'potential' replacement for the 6JB6. It is the same
base, slightly higher transconductance, BUT considerably higher
interelement capacitances. So they 'may' work, especially on the
lower bands, but neutralization may be problematic. It may be
necessary to increase the value of C65 to bring the adjustment in range.
Don't hesitate to post here if you have more questions!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Henry Vredegoor wrote:
Hello All,
I am new to this list, but reading it for some time now.
I'm in the process of setting up/restoring/repairing a Drake 4C line:
R4C, I own this receiver for 35+ years, proved defective when I
recently switched it on after some years of storage
T4XC, bought recently, sold as being defective
MN4, working OK
MS4, working OK
AC4, currently being refurbished by me
As all items were bought separately, I'm missing bits here and there,
like the screws that mount the AC4 PSU in the MS4 cabinet from the
bottom side.
I assume they are non-metric (M3/M4 do not fit).
Can anybody here on this list please tell me what thread/size they
are, so I can order the right screws?
I could not find any info on this in the documentation.
I too have a second question.
With the AC4 came four spare tubes, supposedly usable as a
replacement for the 6JB6A power tube, type 6JF6
Is this a direct "drop-in" replacement for the 6JB6A in the Drake
T4XC or would I have to change (many-) things in the PA circuit
(neutrodynisation etc.) to be able to use these?
Any help appreciated.
73's,
Henry - PA0HJA
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