ACOM Amplifier Support

Fault codes, diagnostics, and service reference for ACOM linear amplifiers

This reference is compiled from forums, user feedback, social media reports, and service documentation. Errors are possible — always verify against your amplifier's official user manual. Never attempt service unless you are a qualified technician.

Common support information covering ACOM 1000, 1200S, 1500, and 2000A amplifiers. Always disconnect mains power and wait 30 minutes before opening any ACOM amplifier — high voltages up to 3000V are LETHAL.

ACOM 1500 Auto-Protection Signatures

The ACOM 1500 stores the 7 most recent auto-protection trip signatures in nonvolatile memory. Each signature is a pair of screens (nA / nB) with 36 symbols total. Read them via OFF LINE mode (press OPER button).

First Group Decode (nA, first 6 symbols)

Position	Value	Meaning
1	1A-7A	Trip sequence number (1 = latest)
2-4	PN0	POWER-ON tests before HV PN2 = POWER-ON after HV + 1s
2-4	SB0	STANDBY during warm-up SB2 = STANDBY after warm-up
2-4	PR0	Entering OPERATE PR2 = During OPERATE
2-4	TR0/2	Antenna relay Rx→Tx / Tx→Rx TR4 = during Tx • TR6 = during Rx
6	1-9, B-F	Trigger parameter (see below)

Trigger Parameter Legend

Code	Signal	Description
1	pfwd	Peak forward power (analogue)
2	rfl	Reflected power (analogue)
3	inp	Input / drive power (analogue)
4	paav	Peak anode alternate voltage (analogue)
5	g2c	Screen grid current (analogue)
6	ipm	Plate current (analogue)
7	hvm	High voltage (analogue)
8	temp	Exhaust air temperature (analogue)
9	g1c*	Drive power present on control grid
B	ORC	Output relay closed (logic)
C	ARCF	RF arc fault (logic)
D	G1C	Control grid current too high (logic)
E	PSE	+24V supply error (logic)
F	LAIR	Low airflow (logic)

Example: 1ATR4B = latest trip (1A) during Tx OPERATE (TR4), output relay closed signal failing (B).

Protection Levels

Level	Name	Effect	Action
1st	WARNING	Message only, TX continues	Monitor and reduce drive
2nd	SOFT FAULT	Trips to STANDBY	Correct conditions (reduce drive, fix SWR)
3rd	AUTO PROTECTION	Trips to OFF LINE	Read signature, contact dealer

The 6dB input attenuator is inserted automatically ~1s after a bad tuning is detected above 20W drive. It resets on PTT release.

ACOM 1000 & 2000A Fault Codes

These models display fault codes on the front panel VFD. Common codes:

Display	Meaning	Likely Cause
GRID	Excessive grid current	Overdrive, bad tuning, tube aging
HV	High voltage fault	PSU issue, rectifier failure, filter cap aging
TEMP	Over-temperature	Fan failure, blocked air filter, extended high-duty TX
SWR	High antenna SWR	Antenna or feedline problem
ARC	RF arc detected	Damage in tank circuit or antenna system
PWR	Overdrive / excessive power	Reduce transceiver drive level
bAtt	Backup battery low	Replace BR1225 (2000A) or CR2032 (1000)

Common Failure Modes

Tube Failures (1000, 1500, 2000A)

Symptoms: Low output, high grid current, unstable bias, red-plating
Expected life: 6000-15000 hours depending on duty cycle
Replacement: Always replace as matched pair (2000A). Use genuine ACOM-stocked tubes or Chinese GU74B/4CX800A
Bias check after replacement: Service menu with RP1 (70mA) and RP2 (250mA) trimmers

HV Filter Capacitor Aging (1000, 1500, 2000A)

Symptoms: Increased hum on output, reduced power, HV fuse blowing
Fix: Replace 8x electrolytics on HV filter PCB with same value/voltage rating
Value: Typically 100-220uF/300-450V depending on model

Vacuum Relay K1 (all models)

Symptoms: Noisy switching, intermittent TX/RX, increased SWR
Fix: Replace with same vacuum relay type (793-P-1C or equivalent)
Note: Do not use conventional open-frame relays — QSK requires vacuum type

LDMOS Failure (1200S)

Symptoms: No output, excessive current, protection tripping
Fix: Replace BLF188XR with MRFX1K80HR5 (drop-in upgrade)
After replacement: Re-bias gate voltage via RP1 for 0.9A idle current

Fan Failure (all models)

Symptoms: Overheating, thermal trip after short TX periods, noisy operation
Fix: Replace 24V fan. Check LM335Z temperature sensor on 1500
Preventative: Clean foam air filter annually (more often in dusty environments)

Backup Battery (1000, 2000A)

Symptoms: Settings lost on power cycle, "bAtt" warning
2000A: BR1225-1HC or BR1225T2-1 (3V, 38mAh)
1000: CR2032

Fuse Reference

Always disconnect mains and wait 30 minutes before accessing internal fuses.

Model	Location	Type	Rating	Size
1200S	Rear panel (mains)	Fast-acting	10A/250V (200-240V) 16A/250V (100-120V)	5x20mm
1200S	Internal (PSU)	Fast-acting	2x 6.3A/250V	5x20mm
1500	Rear panel (mains) x2	Fast-acting	16A/250V (200-240V) 20A/250V (100-120V)	6.3x32mm
	Internal MAINS PCB	Time-lag	0.2A/250V	5x20mm
	Internal MAINS PCB x2	Time-lag	2A/250V	5x20mm
1000	Rear panel (mains)	Fast-acting	10A/250V (200-240V) 16A/250V (100-120V)	5x20mm
1000	Internal	Time-lag	As per model	5x20mm
2000A	Rear panel (mains)	Fast-acting	10A/250V (200-240V) 16A/250V (100-120V)	5x20mm
2000A	Internal HV	Time-lag	As per model	5x20mm

Bias Adjustment

Bias adjustment requires the amplifier open and powered — LETHAL VOLTAGES PRESENT. Only qualified service technicians should perform this.

ACOM 1000 & 2000A

RP1 (BIAS1) — sets low-level idle current: 70mA
RP2 (BIAS2) — sets high-level idle current: 250mA
Located on the MAINS PCB
Access via service menu BIAS function (cycles 3 grid voltage steps)

ACOM 1500

RP1 (50k trimmer) — low-level bias: 70mA
RP2 (50k trimmer) — high-level bias: 250mA
Located on MAINS PCB, G1/G2 header JP4 area

ACOM 1200S

RP1 — gate bias trimmer (10-turn blue)
Sets LDMOS gate voltage for ~0.9A idle current
On PA control board (top deck PA1 F2 V4)
For MRFX1K80HR5 upgrade: target ~2.6-3.1V gate voltage

Model Comparison

Parameter	1200S	1500	1000	2000A
RF Device	BLF188XR LDMOS	4CX1000A tetrode	4CX800A tetrode	2x 4CX800A tetrode
Output Power	1200W	1500W PEP	1000W	1500-2000W
PSU Type	Switched-mode	Linear HV + uA723 screen reg	Linear HV	Linear HV 3.5kVA
Display	LCD + encoder	OLED (VFD older)	VFD	VFD + RCU TFT
CPU	Proprietary MCU	80C552-family	80C552	80C31 + Z86E04
Bandswitch	Relay matrix	S1A-S1C manual	S1A-S1C manual	Stepping motors M3-M5
Frequency	1.8-54 MHz	1.8-54 MHz	1.8-54 MHz	1.8-24.5 MHz (+28 mod)
Backup Battery	CR2032	NVRAM (no battery)	CR2032	BR1225-1HC

Support Contacts

Region	Contact	Details
Worldwide	ACOM Ltd. (Bulgaria)	www.acom-bg.com • support@acom-bg.com
USA/Canada	DX Engineering	www.dxengineering.com • ACOM spare parts stocked
UK	ML&S / Martin Lynch & Sons	www.hamradio.co.uk
Europe	Authorised dealers	Check www.acom-bg.com for local dealer list
Parts	ACOM Spare Parts	acom-bg.com/support/spare-parts

ACOM Bulgaria stocks spare parts for models up to 20+ years old. Tubes and vacuum relays are also available from RF Parts Co. and DX Engineering.