Recently scored a Heathkit IG-5218 Audio Signal Generator in surprisingly good cosmetic condition. It was advertised as working but we all know what that means when Ebay is involved.
Did a cursory inspection inside before power up and the solder work is respectable and clean. Powered on and no sine wave signal output regardless of any knob/switch setting. The fine output level adjustment only nets a meter reading around the "2" position on the meter at full clockwise. The meter needle pulses when some of the "frequency" or "multiplier" knob(s) are turned. With power on, the board mounted lamp is extinguished. I would have thought it would be lit. That's as far as I have gotten so far with troubleshooting. I have a copy of the manual for the IG-18 that has a section on troubleshooting in it. I will start there as soon as I have time to continue with fault isolation.
Any tips from the forum would be helpful and welcome. I really want to get this thing working.
Thanks in advance.
Did a cursory inspection inside before power up and the solder work is respectable and clean. Powered on and no sine wave signal output regardless of any knob/switch setting. The fine output level adjustment only nets a meter reading around the "2" position on the meter at full clockwise. The meter needle pulses when some of the "frequency" or "multiplier" knob(s) are turned. With power on, the board mounted lamp is extinguished. I would have thought it would be lit. That's as far as I have gotten so far with troubleshooting. I have a copy of the manual for the IG-18 that has a section on troubleshooting in it. I will start there as soon as I have time to continue with fault isolation.
Any tips from the forum would be helpful and welcome. I really want to get this thing working.
Thanks in advance.
First you check the power supply voltages. Some heathkit manuals show you what the voltages should be at various points in the circuit. Measure and compare those.
If the issue is not a cold solder joint or assembly mistake a decent question is how could it be damaged. As it only has an output you might check to see what is happening going into the level control and forward to the output.
If the issue is not a cold solder joint or assembly mistake a decent question is how could it be damaged. As it only has an output you might check to see what is happening going into the level control and forward to the output.
Hi slipstream55,
Do you have an oscilloscope?
The lamp does not light. It is used for amplitude stabilization.
-Chris
Do you have an oscilloscope?
The lamp does not light. It is used for amplitude stabilization.
-Chris
Thanks. I do have a scope but not much time to fault isolate other than simple checks at this time. Question: I would like to remove the knobs for cleaning but the manual alludes that they are more or less permanently installed. True?
Operation Manual
Check all DC voltages. Report any not-right.
As said: the lamp on the sine section will NOT light (unless something is way-wrong, maybe not even then). Its grandfather H-P 200AB ran a 230V lamp at about 16V, glow too dim to see in the dark. If broken, no PFB and no oscillation... a 1K resistor should throw it into violent oscillation, a right-lamp needed for proper operation.
Check all DC voltages. Report any not-right.
As said: the lamp on the sine section will NOT light (unless something is way-wrong, maybe not even then). Its grandfather H-P 200AB ran a 230V lamp at about 16V, glow too dim to see in the dark. If broken, no PFB and no oscillation... a 1K resistor should throw it into violent oscillation, a right-lamp needed for proper operation.
Update:
Had time to do 3 quick checks under the "Tests and Adjustments" section of the IG-18 manual as follows:
Black Binding Post to TP1 of Wave Generator Board = 1900 Ohms (approx.)
AC Power cord leads (Switch Off) = Infinite Ohms (approx.)
AC Power cord leads (Switch On) = 50 Ohms (approx.)
This was with my analog meter. I will retake readings with my Fluke this evening.
Had time to do 3 quick checks under the "Tests and Adjustments" section of the IG-18 manual as follows:
Black Binding Post to TP1 of Wave Generator Board = 1900 Ohms (approx.)
AC Power cord leads (Switch Off) = Infinite Ohms (approx.)
AC Power cord leads (Switch On) = 50 Ohms (approx.)
This was with my analog meter. I will retake readings with my Fluke this evening.
Update:
I confirmed the readings in post #7 with my Fluke.
Additionally, the following checks were made:
Line cord prong 1 to chassis = OL
Line cord prong 2 to chassis = OL
Line cord Gnd prong to chassis = 0 Ohms
Black Binding Post to TP1 (power ON) = ~40.65 VDC (S/B 43 VDC)
Next up is the Adjustments section of the manual.
I confirmed the readings in post #7 with my Fluke.
Additionally, the following checks were made:
Line cord prong 1 to chassis = OL
Line cord prong 2 to chassis = OL
Line cord Gnd prong to chassis = 0 Ohms
Black Binding Post to TP1 (power ON) = ~40.65 VDC (S/B 43 VDC)
Next up is the Adjustments section of the manual.
Update:
Got some more checks made and started the Adjustment section of the assembly manual as follows:
P/S board, Q10 voltages:
C = 50.29VDC (S/B 47VDC)
B = 41.32VDC (S/B 41VDC)
E = 40.72VDC (S/B 43VDC)
Adjustments:
Bias, Feedback, Symmetry and Meter Cal pots to center position.
Multiplier = X10
Tens = 10
Units = 0
Freq Cntrl = 0
Sine Wave and Square Wave Coarse/Fine controls = !0 and Full CW
600 Ohm Load switch = EXT
Feedback pot adjusted from ~2.0 VDC to 7.0VDC.
Meter Cal pot adjusted so that DMM reads 5.94VAC at Sine Wave output jacks and panel meter reads same as DMM, 5.94VAC.
DMM removed. Sine Wave Fine output control set to 3PM. Tried to adjust Bias pot for 10VAC panel meter indication. Min/Max adjustment had no effect on meter panel which stayed on 5.94VAC. Note that the Meter pot did adjust to 10VAC with Fine control set to full CW.
Where should I start looking for the Bias pot adjust problem not letting me go to 10VAC on panel meter?
Also, can the knob inserts be removed? The Sine Wave Fine control knob is off by one position in the CW direction.
Thanks for your help in advance.
Mark
Got some more checks made and started the Adjustment section of the assembly manual as follows:
P/S board, Q10 voltages:
C = 50.29VDC (S/B 47VDC)
B = 41.32VDC (S/B 41VDC)
E = 40.72VDC (S/B 43VDC)
Adjustments:
Bias, Feedback, Symmetry and Meter Cal pots to center position.
Multiplier = X10
Tens = 10
Units = 0
Freq Cntrl = 0
Sine Wave and Square Wave Coarse/Fine controls = !0 and Full CW
600 Ohm Load switch = EXT
Feedback pot adjusted from ~2.0 VDC to 7.0VDC.
Meter Cal pot adjusted so that DMM reads 5.94VAC at Sine Wave output jacks and panel meter reads same as DMM, 5.94VAC.
DMM removed. Sine Wave Fine output control set to 3PM. Tried to adjust Bias pot for 10VAC panel meter indication. Min/Max adjustment had no effect on meter panel which stayed on 5.94VAC. Note that the Meter pot did adjust to 10VAC with Fine control set to full CW.
Where should I start looking for the Bias pot adjust problem not letting me go to 10VAC on panel meter?
Also, can the knob inserts be removed? The Sine Wave Fine control knob is off by one position in the CW direction.
Thanks for your help in advance.
Mark
Hi Mark,
You are going to have to be able to hook around the insert and apply enough pressure to pull it out. Warming up the insert might allow it to come out more easily, but be careful about heating the insert up too much. Those things were designed to go in and stay in no matter what. I've never seen an insert come out ever, and I used to collect Heath test equipment. My wife cured me of that illness.
I really wish you luck with this.
-Chris
Oh ... ugly!
You are going to have to be able to hook around the insert and apply enough pressure to pull it out. Warming up the insert might allow it to come out more easily, but be careful about heating the insert up too much. Those things were designed to go in and stay in no matter what. I've never seen an insert come out ever, and I used to collect Heath test equipment. My wife cured me of that illness.
I really wish you luck with this.
-Chris
Question:
In the "Adjustments" section of the IG-18 manual with all of the front panel and PCB controls set per the manuals instructions, the METER CAL adjustment seemed to go well with a reading of approximately 5.62VDC on both the panel meter and the DMM. The BIAS control is then supposed to be adjusted for a maximum panel meter reading though the panel meter may vary erratically, which is normal).
What is considered the value for "maximum" panel meter reading? When adjusting the BIAS control full CCW to full CW there seemed to be no change on the panel meter reading of 5.62VDC other than a very slight blip of the meter.
I may have a problem here. Thanks for any help in advance.
Mark
In the "Adjustments" section of the IG-18 manual with all of the front panel and PCB controls set per the manuals instructions, the METER CAL adjustment seemed to go well with a reading of approximately 5.62VDC on both the panel meter and the DMM. The BIAS control is then supposed to be adjusted for a maximum panel meter reading though the panel meter may vary erratically, which is normal).
What is considered the value for "maximum" panel meter reading? When adjusting the BIAS control full CCW to full CW there seemed to be no change on the panel meter reading of 5.62VDC other than a very slight blip of the meter.
I may have a problem here. Thanks for any help in advance.
Mark
Can you post the IG-18 setup instructions that you are following? There are two methods, and some of us can't remember either one, or not in detail.
The OUTPUT measurement I suspect should be V AC. The panel meter is a DC instrument but the circuitry makes it read the AC value of the output.
The OUTPUT measurement I suspect should be V AC. The panel meter is a DC instrument but the circuitry makes it read the AC value of the output.
I was following Method 1 (DMM) and you are correct. It should be 5.62 VAC. Method one has the user make the adjustments/take readings with a DMM only. No Scope. I didn't have time to set my scope up before I left for a short business trip.
I'm planning on re-capping this IG-5218 and I would like to replace the 4 adjustable potentiometers with Bourns pots. I have values of 750 Ohms (BIAS and FEEDBACK) and 10K ohms (SYMMETRY and METER CAL) showing on the schematic. Can anyone tell me what the wattage rating should be for these? I don't have a parts list and the schematic doesn't provide that info.
Thanks n advance.
Thanks n advance.
Hi slipstream55,
And why are you replacing the original pots? They are fine. 1/2 watt should do if you really must do this.
-Chris
And why are you replacing the original pots? They are fine. 1/2 watt should do if you really must do this.
-Chris
Neither Bias or Meter pot is at all fussy.
There is a feedback pot which is hyper-fussy. I'm not sure a 10-turn would be much help.
There is a feedback pot which is hyper-fussy. I'm not sure a 10-turn would be much help.
Hi .. Not exactly sure the IG-5218 is similar to the IG-18 (but an internet search indicates that this could be the case) ... If that is so a former diya member (richiem) extensively re-worked this Heathkit and made it into a very low distortion oscillator. Tips & descriptions are here:
Modifications: Heathkit IG-18 Audio Generator
Cheers,
Jesper
Modifications: Heathkit IG-18 Audio Generator
Cheers,
Jesper
Thanks for the mod link, Jesper. I plan on doing some upgrading to the unit but I need to get it working first.
Everyone else...thanks for the comments so far.
Everyone else...thanks for the comments so far.
Update:
The BIAS control definitely does not move the panel meter from approximately 5 VAC when adjusted. I was expecting some min/max reading on the panel meter. I measured across the BIAS pot when going full CCW to full CW and am getting a reading 0f 0.00 VAC.
Anyone got any ideas where to go from here?
Thanks.