3 different tubes where used in the units, JAN 8930, Amperex DX 393, Eimac X6512.
WB0TEM has used a 4cx250B by making an adapter to compensate for the
different size of the plate fins.
The AM-6154 can be used on 432 MHz by using the wa5vjb mod to the input
relocating the pedestal inductor.
The AM 6155 can be used on 144 MHz by replacing the pedestal inductor with
k0tlm mod.
The AM 6155 can be used on 220MHz using N3AHI mod to the input circuit
The AM 6155 can be used on 432 with either the K0TLM or WA5VJB mod to input.
Contact them for more info.
The following info is a collection of material from N3AHI, WB5NMA, WA4JQV,
K0TLM, WA5VJB &, KF0M.
CHASIS WIRING AM5154 - 6155
Disconnect all wires from the tune/operate switch, S3.
This switch will be used as a stby/opr switch.
Note: 2 red wires will be removed from S3, one wire connects to tie point
E8. The free end of this wire should be routed to J3 pin 9. The other red
wire goes to J6 pin 4, the end free end of this wire should be routed and
soldered to E-8.
One of the blue shielded wires attached to TB2 goes to J7pin 6 on rear of
the unit. This wire can be used to run from 1s3 the stby/opr switch to the
key jack on the back of the unit.
METER UNIT
Clip jumper wire between S1A pins 1 and 3.
Move wire from S1A pin 11 to pin3. This wire should also go to pin 16 p1.
This makes the key position display screen reg. current
BUFFER AMP/MULTI FUNCTION ELECTRICAL INS. A5 BOARD
Remove C1 to speed up meter response in fwd power position.
Change R3 from 2.7k-15k 1/4watt to keep meter from pegging in forward power
position with higher output power.
CR4 remove from board prevents meter error.
CR6 If installed on pc board, remove. On some units, cr6 is installed on s1
the meter switch. if cr6 is on the meter switch leave it in place.
R4 5.1k may need to be changed to 22- 28k to make rev/fwd pwr positions
function correctly.
CR4 & CR6 are the meter protection diodes. when left as shown on the
schematics, they can conduct enough microamps to cause as error in plate
current , plate voltage and, screen current readings. The plate current
error can be as much as 40%. CR4 should be installed DIRECTLY across the
pos. and neg. terminals on the meter. If CR6 is was found on the pc board
and removed it should also be installed directly across the meter. The
cathode or band of CR4 should be cinnected to the neg. terminal of the
meter. The installation of CR6 is OPPOSITE, the cathode or band should be on
the pos terminal with anode on the neg. terminal.
This change will result in a higher accuracy for the meter readings in all
positions except fan and heater. the fan position is strictly a relative
indication. The value of R18 can be increased if desired to return the
heater voltage reading to a nominal 24.
The V-LPA position is unused after all mods have been made
R7 should be adjusted for zero while in forward power with no drive
applied.R26 & R22 should be adjusted for 3/4 scale at full power out. R9
should be adjusted for zero in rvs pwr with no drive applied.
PLATE SCREEN PWR SUPPLY BOARD
Depending on the individual amp, the plate voltage meter may be in error. In
most case this can be corrected by measuring the individual voltage drops
across resistors R4-R8 and swapping R8 with appropriate one of R4-7 to make
the plate voltage read higher or lower as required. Use extreme caution when
taking voltage readings of the individual resistors.
In some cases the value of R11 must be changed experimentally to get the
plate voltage to read correct.
The HV can be turned on with the cover removed by pulling up on the
cover interlock switch S1.
On most amps the pc board has been covered with a conformal coating
which can make soldering and voltage measurements difficult.
AM6154 INPUT TUBE BASE
Replace R2-R5 (cathode to ground) with 22 ohm 1/2w carbon comp or larger 2w
resistors. The 1/4w units will overheat at amateur power levels.
The fuse that powers the grid xfmr should be replaced with a smaller value.
If one of the diodes shorts on the ac-ac converter board +14v supply, the
xfmr will not pull enough current to blow the blue print fuse and will cause
the xfmr to burn up. Info from KB8JI.
The AM 6155 can be used on 2 meters by using the input circuit in
the 1987 handbook for a 2mtr 8930 amp.
if the orange kapton dielectric disc for the plate blocking cap,
c15, shorts out it can be replaced with teflon. if you clean the parts for
c15 you will probably not have any problems.
Some people have had problems with E1 arcing under normal operating
conditions the function of E1 is to conduct only in a plate to screen short
to protect the screen supply. The function of these devices is described in
the w2gn articles about the across 4cx250b amps published in Ham Radio Mag.
Some units have an extra module installed on the blower inlet to sense a
failure of the blower.
These mods allow the use of an internal +15 VDC supply to power control
circuits that originally were power by +20 VDC from the exiter.