On Sat, 19 Mar 2005 21:27:20 -0800, Mike wrote:
I don;t really expect to get any help on this but figured what the
heck
BK E-200D RF signal generator - powers up, crystal calibrator seems to
work but meter doesn't budge and no RF out. help.
The manual including schematic is available he
ftp://bama.sbc.edu/downloads/b&k/e200d/
Check the power supply. The PCB board etchings on the unit I have show
10.6V & 10.0V as the two B+ supply voltages. The schematic shows 10V &
9V. After I got mine working I found the schematic voltages were more
correct. I get 9.93V at the 10V point & 8.82V at the 9V point.
Here is a snippet of PS in ASCII (use fixed pitch font):
Transformer +--------(+10V)
Pri. Sec. |
):+----||-+---+--68R--+--47R--+-(+9V)
)
14.0R | | 200mW | 23mW |
):+-+ | | | |
)
|15.6R | 200uF ZD 200uF
):+-|--||-+ 25V 10V 25V
| | | |
_|_ _|_ _|_ _|_
The transformer secondary measures 14-15 ohms on each side to Gnd.
Both resistors (68R & 47R) had drifted with age. The 68R going to
95ohms. I replaced both resistors. The 68R should be at least 1/2W, the
47R could be 1/4W.
Actually I started off replacing all the electrolytics & these two
resistors. There are 9 electrolytics, 7 on the bottom PCB, one on the
meter, & one inside the top osc. section.
The following is from my notes:
Color C# uF V Schematic replacement
-----------------------------------------------------------------
Gray - C31 -200uF,25V 220/??V 220uF,35V
Gray - C32 -200uF,25V 220/??V 470uF,16V
Gray - C30 - 47uF,10V 50/??V 47uF,16V
Gray - C33 - 47uF,10V 50/??V 47uF,16V
Gray - C34 - 47uF,10V 50/??V 47uF,16V
Blk - C28 - 10uF,25V 10/??V 10uF,25V
Blk - C40 - 10uF,25V 10/??V 10uF,25V
On the meter:
Gray - C55 - 47uF,50V 50/25V 47uF,50V
In the OSC (top, shielded PCB):
Gray - C13 -100uF,12V 100/??V (2ea.,paralleled) 47,10V
Here is the location of most devices on the main (bottom) PCB:
+-------------------------------------------------------------+
| - |
| C33 |
| + 47uF |
| C34 10V |
| 47uF + |
| 10V |
| - |
| |
| |
| - |
| C28 |
| 10uF |
| x 25V |
| 4 + |
| 7 |
| -200uF,25V+ R |
| - x |
| C40 x68Rx + |
| 10uF -200uF,25V+ C30 |
| 25V 47uF |
| + 10V |
| - |
+-------------------------------------------------------------+
After replacing the above everything was working pretty well.... The
internal audio osc. was not working. I had to tweak R42 (1K pot) to get
any tone, then set it to 400Hz.
The above got mine back to what seems to be OEM status. Everything
seems to work properly. I'm not sure of the output levels on each band
as I have no way of checking RF levels accurately. All the resistors in
the attenuator section were very close to perfect (still within 5%)!
If you have problems after getting rid of obvious defects the schematic
has voltage levels that should be close.
One other note: The 1MHz marker is xtal controlled & the 100KHz marker
is calibrated to the xtal marker. It seems the OEM PCB layout &
silkscreening had both the markers running full time (for stability) &
their outputs were switched in as needed. This extra noise probably
caused unexpected "birdies" at the output even when the marker outputs
were not switched in (markers not shielded). The wiring on my unit
reflects changes (as does the schematic) that disconnects power to both
marker oscillators except when they are switched in.
All this is no problem except the PCB silkscreening does not match
component placement is the marker area.
I only found this out when I added a trimmer cap in series with the
1MHz xtal to set it more exactly at 1,000,00x Hz (haha - If my freq
counter is still relatively accurate). I started with a 8-50pF trimmer &
could get 1,000,00x Hz only at the 50pF setting. Adding a 15pF in
parallel with the 8-50pF trimmer allowed a nice adjustment range about
+60/-40Hz (999,960-1,000,060Hz).
When I got this unit the meter was 1/3 full of water
It had been
rained on!! It had not been outside long (I think just rain 1 time) but
it is fine now. Good luck
Kim Clay
PS: There are five internal pots shown below. The only one I know about
is R42, the audio osc. pot (sets audio freq). If anyone has info on
setting the others I would like to know - thanks! kc
Internal Pots: not externally adjustable;
R42 - 1K - "Audio Osc." - 400Hz bridged "T" osc freq setting.
R54 - 10K - "Mod Cal" per schematic.
Internal Pots: externally adjustable via holes in back chassis
(facing back, Left-to-Right);
R28 - 30K, Mixer Adjust
R50 - 50K, "RF Threshold"
R48 - 1K, "Carrier Cal"