the following text is a little bit longer then usual and therefore
it may be some lines to read, but as i had some requests to hold
my FS-4 related comments public rather that private, i will do
so.
For the readers that are uninterested in the one or other topic,
i
apologize in advance for stressing your patience - in no way it's
my intention to be annoying or intrusive.
First, thanks to the various comments on the contact cleaner, it
de-
finitely will try to get DeOxit in England. My personal experiences
with some products from the former "Kontakt Chemie" company are
not
the best in professional circuits. Especially equipment treated
with
"Kontakt 60" showed the trend to reappear with exactly the same
pro-
blems appr. half a year after the cleaning. "Tuner 600" worked
a
little better with this respect, but also not 100% satisfying.
I
cleary have to point out, that my personal experience with this
two
products is now laying years behind - and in the meantime the com-
pany may have changed the receipe of this products significantly
without changing the name. My best experience with contact cleaners
in the past has been the product "Rivolta SLX1000" from a company
named "Bremer & Leguil", but due to more stringent environmental
regulations in Europe, this product no longer is on the market,
and the successor of this product by far does not match the per-
formance of "SLX1000" for RF and other electronics stuff. So, if
you should have the one or other can from "SLX1000", keep them
like gold. To my knowledge, this also in the past was the pre-
ferred product by a bunch of professional companies like R&S,
amongst others - and the usually select very careful, what they
use. In Germany, there is another product available, which looks
very promising and which will undergo a detailed test by me, if
it finally will arrive here (i have ordered five cans). The name
of this product is "EML200F" from "Electrolube". If of any interest,
i will post the results of my tests here in this forum - please
let
me know. In Germany this contact cleaner (it is labeled to be a
"con-
tact cleaning oil") is sold by the company "Rainer-Förtig
Elektronik".
A 200[ml] can goes for EUR 7,95. The link to their homepage is
(you
have to scroll down to the bottom of this page):
http://www.rainer-foertig.de/Bastler-Geraete.htm
Please note, that i do not have any affiliations nor do i have any
other commercial interest in / with the companies i mentioned above.
I just wanted to make live easier for the readers of this lines
by
providing "where to get" information. The same statements goes
also
for the companies that i am naming below in the FS-4 section.
So, now for some FS-4 comments:
First of all, it may be a tricky job, to obtain some of the semicon-
ductor parts for this synthesizer. So, i will do some comments
on the
individual parts:
- MC1733 (U1): Obsolete part from former "Motorola Semiconductor",
now
"ON semiconductor". This is a 200[MHz] differential
amplifier with some selectable, fixed gain settings.
If of any interest, i can scan the datasheet and dis-
tribute it as a PDF-file. This part may be obtained
from "Rochester Electronics" (www.rocelec.com), where
ONSemi / Motorola states that they would be their
official source for obsolete parts. The location of
this IC is on the "A100 VCO-Board"
- MC4044 (U2): Obsolete part from former "Motorola Semiconductor",
now
"ON semiconductor". This is the phase detector for the
PLL. If of any interest, i can scan the datasheet and dis-
tribute it as a PDF-file. A 1:1 drop-in-replacement is
the MC4344, which, however, is also obsolete. This part
may be obtained from "Rochester Electronics"
(www.rocelec.com), where ONSemi / Motorola states that
they would be their official source for obsolete parts.
A reason for this chip to die may be a minor design
flaw of the FS-4: The pins 5 and 10 of this chip are
tied together without any current limiting resistors
which is in clear contrast to the Motorola application
note "AN535" (although this apps-note is using a MC4344).
Thus, these both ouputs may "fight" against each other,
possibly resulting in substantial short circuit currents
at this point. A suggested cure here will be:
- open the connection between pin 5 and 10 of this IC.
- leave R319 (8.2[K]) connected to pin 5.
- connect an additional resistor with 8.2[K] to pin 10
and the other end of that resistor to the base of Q303
(2N3392).
All this stuff is located on the "A300 Digital Board"
Please note, that in that region at least two different
versions of the FS-4 have been built: One, where Q303
is the only amplification transistor in the loop filter,
and a second one (which i assume is the later on), where
Q303 has been followed by Q304 (2N3404) in order to
obtain a larger DC-gain in the loop filter.
- SN7490 (U1): This chip is still available from a German
broadline
electronics distributor, which also has a sales office
in the Unites States (i double checked during a phone
call with the lady there, that they also will sell in
single quantities and also to individuals). The link
to their homepage is:
http://www.buerklin.com/default.asp?l=e
The order-number of this IC is: 45S2300 (SN7490AN).
This IC is located on the "A300 Digital Board".
- SN7408 (U4): This chip is still available from a German
broadline
electronics distributor, which also has a sales office
in the Unites States (i double checked during a phone
call with the lady there, that they also will sell in
single quantities and also to individuals). The link
to their homepage is:
http://www.buerklin.com/default.asp?l=e
The order-number of this IC is: 44S8850 (SN7408N).
This IC is located on the "A300 Digital Board".
- SN7486 (U5): This chip is still available from a German
broadline
electronics distributor, which also has a sales office
in the Unites States (i double checked during a phone
call with the lady there, that they also will sell in
single quantities and also to individuals). The link
to their homepage is:
http://www.buerklin.com/default.asp?l=e
The order-number of this IC is: 45S2200 (SN7486N).
This IC is located on the "A300 Digital Board".
- SN74192 (U3): This is the programmable frequency divider an there-
fore it could not replaced by a functional "similar"
substitute, it has to be EXACTLY the same function
(neither '191 nor '193 TTL-family-members will work here,
as they are counting binary whereas the '192 counts BCD!).
However, the bipolar and low power schottky (LS) as
well as the ALS and HCT variants of this chip are
hard to get. So, i suggest, to replace this chip by
an 74HC192 (which is a 1:1 drop in IC) and add the
following modifications to the FS-4 in order to main-
tain the correct logic levels for the 74HC192. As this
is a high-speed-CMOS-IC, also the power-supply pins of
this chip must be locally bypassed, which is also in-
cluded in the modification described below:
- Add a 4.7[K] resistor between pin 1 and pin 5 of
this IC. This is a pullup resistor for pin 1 to
+5[V].
- Add a 4.7[K] resistor between pin 9 and pin 5 of
this IC. This is a pullup resistor for pin 9 to
+5[V].
- Add a 4.7[K] resistor between pin 10 and pin 5 of
this IC. This is a pullup resistor for pin 1 to
+5[V].
- Add a 0.1[uF] ceramic capacitor between pin 8 and
pin 16 of this IC. This bypasses the +5[V] supply
locally at this chip. Keep the capacitor leads as
short as possible (low inductance) and use a capa-
citor with good rf-characteristics (i.e. X7R cera-
mic material).
- Cut the connection between U2 (MC4044) pin 3 and
the junction of pin 11 & pin 13 of this IC (U3,
74192). Install a 47[Ohms] resistor between U2
(MC4044) pin 3 and the junction of pin 11 & pin 13
of this IC (U3, 74192). Keep the lead-lenth of the
resistor at this junction as short as possible in
order to avoid the radiation of high frequency
noise. The purpose of this resistor is to incor-
porate some damping of the divided signal before
entering the phase detector, as this signal exhibits
much faster switching speeds (due to the high speed
CMOS technology) than the one from it's bipolar pre-
decessor.
Be careful in doing all that work, since this is a CMOS-
chip which is subject to damage due to static discharge.
Use standard CMOS precautions.
This HCMOS-replacement chip is still available from a
German broadline electronics distributor, which also
has a sales office in the Unites States (i double
checked during a phone call with the lady there, that
they also will sell in single quantities and also to
individuals). The link to their homepage is:
http://www.buerklin.com/default.asp?l=e
The order-number of this IC is: 63S1950 (MM74HC192).
This IC is located on the "A300 Digital Board".
- MC1496(U402): This chip is still available from a German broadline
electronics distributor, which also has a sales office
in the Unites States (i double checked during a phone
call with the lady there, that they also will sell in
single quantities and also to individuals). The link
to their homepage is:
http://www.buerklin.com/default.asp?l=e
The order-number of this IC is: 41S6810 (MC1496N).
This IC is located on the "A400 Parent Board".
If of any interest, i will continue with a transistor, varactor
diode
and double-balanced mixer section of the FS-4 in the same manner
s
above in a second follow-up-posting in this forum. Please let me
know,
if there is interest in.
Let's continue with the 4-Line dial- and meter-bulbs:
As it is complicated (not to say impossible) to obtain the "GE #47"
bulbs (that Drake used in a lot of their equipment) here in Germany,
i looked for a drop-in-replacement electricalwise and mechanicalwise.
I found one, that at least in my 4-Line stuff (i.e. SPR-4, R-4C,
T-4XC)
is working very well without any problems and without any modifications
(even the 39[Ohms] current limiting resistor in the SPR-4 remained
un-
touched):
Order number 33G200 (bulb 6[V]/180[mA], socket BA 9s) from the same
German broadline electronics distributor as mentioned above in
detail
several times. Once again the link to them:
http://www.buerklin.com/default.asp?l=e
Finally, for the 4-Line knobs:
If anybody has a spare "DAKA WARE" knob for the SPR-4's "MODE"-
switch, i would be glad to buy this. I know, that there is a company
in the USA named "Caltronics", who are selling knobs that are really
close to 1:1 replacements for the original knobs for a number of
4-
line family members, however, they ignored my email and fax inquiry
for larger quantities of those knobs completely (maybe they are
not
interested in a small business to Europe, who knows). Just for
your
interest, here is the link to their knob-page:
http://www.caltronix.com/catalog/cat89.htm
The Drake-compatible knobs are the ones with the order numbers:
- 50-132 (for the R-4C and T-4XC)
- 50-133 (for the SPR-4)
- 50-1418 (shaft reducers for the smaller shaft)
- 50-261 (tuning knob for the 4-line, however without the finger
dell).
If a helpful ham living in the United States is willing to support
me in obtaining those knobs from them and subsequently shipping
them
to me, i would be very glad. Of course i will cover for all expenses.
Please contact me, then i will email you a list of what i want
to
order.
So, this was a lot of stuff to read - thanks for all your patience,
enjoy your weekends and kind regards.
73, Herbert, DG7MCC
