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Author Topic: Ameritron warning-UPDATE  (Read 40544 times)
W1QJ
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Posts: 2984




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« on: October 08, 2013, 01:43:29 PM »

OK, I have this figured out.  I thought the schematic was wrong and the amps were wired according to the schematic and that is why there is the prevailing problem.  Taking a closer look at the wiring I have found the problem.  The problem is with the actual wiring of the amp which DOES NOT follow the schematic.  I have 2 other big box Ameritrons here along with the one I am working on.  The others are Al-1500's which have a 3 minute timer.  Anyhow, The problem is the amps (all of them I have here) are all wired the same way and apparently ALL have the same wiring mistake.  Here is what is wrong.  Relay RLY2 is a contactor relay, double pole and it breaks and makes both sides of the 240v line.  One set of contacts simply breaks the one lead to the transformer.  The other line is "supposed" to go directly to S5 the safety switch.  If S5 is open that line is dead no matter what and no problems can exist.  BUT...That wire from the load side of RL2-2 DOES NOT go to S5.  Instead it goes to the relay contact and R3 junction, therefore that phase is not completely dead as it passes through the 10 ohm resistor.  Since that phase does not go directly to S5 and goes instead to R3 which is tied to the relay coil, there is a voltage that passes through the relay coil and R3 that creates 400vdc in the rectifier etc.  S5 breaks that phase AFTER the relay coil.  And that is the way the amps are wired.  I would have to conclude that as far as I can see ALL amps are wired this way which would lead me to believe ALL amps would have the same problem.  The 3 units I have here are all wired wrong. Hence, the proper fix is to  remove the wire from S5 which goes to the terminal strip to pick up the black/white transformer lead.  Remove the blue/white wire from the relay/R3 junction and move it to S5, then move the wire that was on S5 to where the blue/white wire was.  Moving the wires accomplishes the same task BUT...in doing so the relay coil cannot be energized and pass the voltage thru the coil on to the transformer.  I haven't tried the other amps but I have to think they will show the same problem.  My conclusion is that most likely ALL amps out there will show the 400vdc if S5 is open and the amp is turned on.  I would like to hear from others if this problem affects your amp.  This could be a universal problem with all 3 amps in that series.  I hope to hear from others if they see this problem with their amps.  Anybody out there have a rather new one they can test? 
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9A4WY
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Posts: 30




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« Reply #1 on: October 08, 2013, 11:01:40 PM »

OK, I have this figured out.  I thought the schematic was wrong and the amps were wired according to the schematic and that is why there is the prevailing problem.  Taking a closer look at the wiring I have found the problem.  The problem is with the actual wiring of the amp which DOES NOT follow the schematic.  I have 2 other big box Ameritrons here along with the one I am working on.  The others are Al-1500's which have a 3 minute timer.  Anyhow, The problem is the amps (all of them I have here) are all wired the same way and apparently ALL have the same wiring mistake.  Here is what is wrong.  Relay RLY2 is a contactor relay, double pole and it breaks and makes both sides of the 240v line.  One set of contacts simply breaks the one lead to the transformer.  The other line is "supposed" to go directly to S5 the safety switch.  If S5 is open that line is dead no matter what and no problems can exist.  BUT...That wire from the load side of RL2-2 DOES NOT go to S5.  Instead it goes to the relay contact and R3 junction, therefore that phase is not completely dead as it passes through the 10 ohm resistor.  Since that phase does not go directly to S5 and goes instead to R3 which is tied to the relay coil, there is a voltage that passes through the relay coil and R3 that creates 400vdc in the rectifier etc.  S5 breaks that phase AFTER the relay coil.  And that is the way the amps are wired.  I would have to conclude that as far as I can see ALL amps are wired this way which would lead me to believe ALL amps would have the same problem.  The 3 units I have here are all wired wrong. Hence, the proper fix is to  remove the wire from S5 which goes to the terminal strip to pick up the black/white transformer lead.  Remove the blue/white wire from the relay/R3 junction and move it to S5, then move the wire that was on S5 to where the blue/white wire was.  Moving the wires accomplishes the same task BUT...in doing so the relay coil cannot be energized and pass the voltage thru the coil on to the transformer.  I haven't tried the other amps but I have to think they will show the same problem.  My conclusion is that most likely ALL amps out there will show the 400vdc if S5 is open and the amp is turned on.  I would like to hear from others if this problem affects your amp.  This could be a universal problem with all 3 amps in that series.  I hope to hear from others if they see this problem with their amps.  Anybody out there have a rather new one they can test? 
If you leave amp with this wiring error on, without cover, for 20-30 seconds relay coil will open up.
Transformer has much less ESR than relay coil...so coil sees higher voltage than 110VAC.you have relay coil+transformer primary in series...so primary sees "VACin"-"coil voltage"= cca 20-30VAC, and then on secondary you see cca 350-400VDC rectified.
Kristian,9A4WY
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W1QJ
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Posts: 2984




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« Reply #2 on: October 09, 2013, 04:12:30 AM »

Kristian. I assume you made the correction by switching the 2 wires I suggested?  Looks like you knew about this already.  Took me a long time to find out about this problem.  Also, I suggest moving the filament transformer primary lead from the line side of the fuse to the load side.
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9A4WY
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Posts: 30




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« Reply #3 on: October 09, 2013, 04:35:58 AM »

Hi Lou...
I couldn't remember what I did...but, for sure , problem is this posted above.
It was a year before maybe??...
Stepstart was still functional after my rewire.
Later...I install another one small relay with simple RC time delay to switch on coil of relay(RLY3) in schematic because I have 16A ultrafast fuse on this main outlet(to save plate transformer if something goes wrong  Wink )...now I can start the amp with 4A mainline fuses... Grin
very smooth "click" after 1 second
Kristian,9A4WY
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KH6AQ
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Posts: 7994




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« Reply #4 on: October 09, 2013, 05:45:49 AM »

This mod should be written in an ISO compliant format. Write it as a list of steps, include color photos or color drawings, and conclude with a test to confirm that the mod has been correctly implemented.

1. Test to determine if the amplifier is wired correctly (a visual check of the wiring or an electrical test of the HV Interlock)
2. Photo of correct wiring
3. Photo of incorrect wiring
4. Step 1
5. Step 2
6. Step 3
7. HV Interlock electrical test





« Last Edit: October 09, 2013, 05:59:28 AM by WX7G » Logged
G3RZP
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Posts: 1319




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« Reply #5 on: October 09, 2013, 06:12:59 AM »

And get an ISO 9000 audit....
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W9FIB
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Posts: 2529




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« Reply #6 on: October 09, 2013, 07:25:36 PM »

I didn't know that ham radio required ISO certification. So much for junk box home brew!  Cheesy
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73, Stan
Wisdom is knowledge you gain after you know it all.
W1QJ
Member

Posts: 2984




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« Reply #7 on: October 10, 2013, 03:21:33 AM »

And get an ISO 9000 audit....

I brought this issue up on the Ameritron amp yahoo group.  Tom W8JI said that there was no law requiring that any interlocks be installed in amps.  We know that the SB-200 does not have one, The Amp Supply LK-500 I don't think has one.  Anyhow, it seemed that because one is not required by law it would not be illegal or maybe the term liability would be a better term if the interlock did not work or was faulty.  My only concern is that all owners of the amps should be aware of the issue.  What Ameritron does about it is their business not mine.  Tom said that the people at Ameritron probably did not know of the problem because it is their protocol not to ever turn amps on with the cover off.  I believe he said there is a warning about that in the manual.  Tell me, am I the only idiot that works on an amp with the cover off? 
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TANAKASAN
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Posts: 933




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« Reply #8 on: October 10, 2013, 05:44:55 AM »

"Tell me, am I the only idiot that works on an amp with the cover off?  "

Maybe, it depends on the circumstances. Here at work we are allowed to work on equipment with the covers off but anything that uses greater than 230V requires:

1) Two engineers present at all times with one working on the equipment and one looking for mistakes.

2) Both engineers standing on thick rubber mats.

3) All tools to be insulated to withstand the voltages in use.

4) A bench emergency cutoff that's always within reach of the second man.

5) EVERYTHING documented before and after and the two engineers add their signatures at the bottom of the paperwork.


Tanakasan
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KH6AQ
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Posts: 7994




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« Reply #9 on: October 10, 2013, 09:23:06 AM »

And get an ISO 9000 audit....

I brought this issue up on the Ameritron amp yahoo group.  Tom W8JI said that there was no law requiring that any interlocks be installed in amps.  We know that the SB-200 does not have one, The Amp Supply LK-500 I don't think has one.  Anyhow, it seemed that because one is not required by law it would not be illegal or maybe the term liability would be a better term if the interlock did not work or was faulty.  My only concern is that all owners of the amps should be aware of the issue.  What Ameritron does about it is their business not mine.  Tom said that the people at Ameritron probably did not know of the problem because it is their protocol not to ever turn amps on with the cover off.  I believe he said there is a warning about that in the manual.  Tell me, am I the only idiot that works on an amp with the cover off?  

I looked at three other manufacturers of amateur radio tube RF amps and they all feature HV Safety Interlocks. From that I assume that the product safety standard that applies to amateur radio RF amplifiers requires this safety feature. If this is so, then the HV Safety Interlock MUST function. For example, UL60950 (information technology equipment) goes into great detail about safety interlocks.

There are AL-82, 1200, and 1500 models that are CE marked. These must conform to the European Union R&TTE directive and this includes safety. EN60215 appears to apply to amateur radio amplifiers.

If a HV Safety Interlock is not a requirement, but the equipment has one and it does not operate correctly, there may still be a problem; Ameritron describes the HV Safety Interlock in the Instruction Manual, leading the user to believe that the HV is OFF when the cover is removed. This creates a situation that invites an electrical shock.

I see two possible fixes: One is to recall the affected amplifiers and fix them so that the HV Safety Interlock works. The second is to issue CE compliant warning stickers to place on the top cover and on the rear of the unit. Both fixes would be advertised for a sufficient length of time in CQ, QST, and on the Ameritron website. If the U.S. CPSC and European Union RAPEX are involved they will list the recall on their website.
« Last Edit: October 10, 2013, 10:14:01 AM by WX7G » Logged
W1QJ
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Posts: 2984




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« Reply #10 on: October 13, 2013, 05:45:51 AM »

UPDATE:  I emailed Ameritron about this.  I got a quick response from Mike.  I was impressed with the quickness.  Anyhow, Mike told me Ameritron is aware of the problem and claimed that the newer units are now wired to eliminate the 400v problem.  He said the fix used was as I initially reported.  Break the tie between coil and adjacent relay connection and move coil wire over to S5.  That does fix the voltage problem but does not satisfy the schematic for the step start circuit.  That fix does not allow for the relay coil to charge through the step start resistor as shown in the schematic.  Thanks to WX7G who was kind enough to run the math, not charging through the resistor reduces the delay time of the relay from about 120ms to 20ms.  This is significant and the extra 100ms gives a bit more charging time to the filter caps.  Also, it appears that if the wiring was done according to the schematic 100%, if the step start resistor opens up the step start relay would not close telling the operator that the resistor is bad.  Wired the other way the relay will still close and no step start action would be accomplished.  It is a fairly common occurrence that the step start relay contacts weld.  Probably due to the lack of the delay time and no resistance in the primary line.  The relay would then need to be replaced.  I have always noticed a very bright spark coming from these step start relays and now I know why.  I've yet to see the starting action of a properly wired step start on these amps.  I intend to properly wire the unit I have here now and re-exam the step start action of the relay and see if the spark gets quenched some.  I would think it would.  So I would have to revise the "fix" to include not only switching the wire on S5 with the blue/white on the step start relay but to also ensure that the relay coil wire gets connected to the load side of the step start resistor.  That will then satisfy the schematic.  So unfortunately I think even the newer units need some additional work or at least to be sure the relay coil is on the load side of the step start resistor.  I doubt it will be.
« Last Edit: October 13, 2013, 05:49:00 AM by W1QJ » Logged
NU1O
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« Reply #11 on: October 13, 2013, 06:17:31 AM »

What do they intend to do with all the defective units they sold?  Hardly a week goes by that I don't read about a product or food recall so I don't understand how they could get away without issuing a recall for those units which were not wired properly and advertising in amateur radio magazines and on the Web.  I would've thought the CPSC and its European counterpart would order them to issue a recall.
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W1QJ
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Posts: 2984




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« Reply #12 on: October 13, 2013, 06:26:41 AM »

What do they intend to do with all the defective units they sold?  Hardly a week goes by that I don't read about a product or food recall so I don't understand how they could get away without issuing a recall for those units which were not wired properly and advertising in amateur radio magazines and on the Web.  I would've thought the CPSC and its European counterpart would order them to issue a recall.

I don't know the answer to that, sorry.  Neither is that my concern.  my only concern at this point is to enlighten owners of these amps that the step start circuit is not wired according to the schematic which hinders its effectiveness,  Many amps do not interlocks nor do they have step start circuits.  If either of these are a necessity or not is not the debate. As far as I am concerned the post should be limited to the technical discussion of step start circuits and not to legal issues.  I am not a lawyer nor play one on TV Grin
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KH6AQ
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« Reply #13 on: October 13, 2013, 07:01:16 AM »

U.S law requires the manufacturer to contact the CPCS and report any unsafe product. A manufacturer cannot legally implement a safety fix or a recall without the CPCS being involved.

Even if there isn't an applicable safety standard requiring a HV Safety Interlock on amateur radio RF amplifiers, the CPCS can still initiate a recall of any unsafe product within their jurisdiction. 

If no injuries or deaths have occurred the CSPS may choose not to recall a product.



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NU1O
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« Reply #14 on: October 13, 2013, 08:44:05 AM »

What do they intend to do with all the defective units they sold?  Hardly a week goes by that I don't read about a product or food recall so I don't understand how they could get away without issuing a recall for those units which were not wired properly and advertising in amateur radio magazines and on the Web.  I would've thought the CPSC and its European counterpart would order them to issue a recall.

I don't know the answer to that, sorry.  Neither is that my concern.  my only concern at this point is to enlighten owners of these amps that the step start circuit is not wired according to the schematic which hinders its effectiveness,  Many amps do not interlocks nor do they have step start circuits.  If either of these are a necessity or not is not the debate. As far as I am concerned the post should be limited to the technical discussion of step start circuits and not to legal issues.  I am not a lawyer nor play one on TV Grin
Lou,

I've read all your posts on this topic and I was under the impression from the start your primary concern was that somebody might attempt to repair one of the improperly wired amps under the impression there was no voltage because a safety interlock was built into the amp and wind up with a potentially lethal shock. I always thought the non-functioning step-start circuit was just an ancillary concern for you. 

The first sentence of your first message reads as follows:

"All owners of a particular run of these amps need to be aware of a potentially dangerous  shock hazard!"

IMO, it seemed your main concern at the start was a potential shock hazard and not the step-start circuit not working properly.

This has been a very interesting read so far.  I don't normally read the amp forum but I'm going to stick around.  I've already learned a lot in the past week or so.

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