Seeburg HFMA1 Amplifier draws excessive current
I’m currently working on a V200 amplifier and can’t figure out where the current draw is coming from. I’ve isolated it to the 6.3 heater circuit but can’t find any issue with it. The only problem is the humidity adjustment is missing the wire wound section so it’s basically not doing anything. I put 2 resistors in place as a replacement but when I fire up the amp my amp meter starts rising and I shut it down between 2 and 3 amps. Usually when texting one of these amplifiers it slowly rises to about 1.5 amps and holds steady there. What am I missing here? Sent from my iPhone
On 2024/03/06 4:57 p.m., M De Simone via Jukebox-list wrote:
I’m currently working on a V200 amplifier and can’t figure out where the current draw is coming from. I’ve isolated it to the 6.3 heater circuit but can’t find any issue with it. The only problem is the humidity adjustment is missing the wire wound section so it’s basically not doing anything. I put 2 resistors in place as a replacement but when I fire up the amp my amp meter starts rising and I shut it down between 2 and 3 amps. Usually when texting one of these amplifiers it slowly rises to about 1.5 amps and holds steady there. What am I missing here?
Start by unplugging all the tubes and see what happens. Then plug half of them in and see if the current is OK...then 1/2 of the remaining tubes...splitting problems in half speeds up the discovery process I find. John :-#)# -- John's Jukes Ltd. 7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 Call (604)872-5757 (Pinballs, Jukes, Video Games) flippers.com "Old pinballers never die, they just flip out"
Hey John, thanks for the response. I’ve tested all the tubes and inserted voltage on the heater line with all tubes removed and it was better but as soon as I start putting in the tubes the current starts drawing more than usual. I still keep thinking back to the hum control pot. Can this affect the current draw if it’s missing? I also believe the output transformer needs to be replaced as resistance readings across the plates of the output tubes and centre tap of transformer differs by about 50%. I don’t think this would affect the heater circuit? Any help appreciated, Mauro Sent from my iPhone
On Mar 6, 2024, at 8:36 PM, John Robertson via Jukebox-list <jukebox-list@lists.netlojix.com> wrote:
On 2024/03/06 4:57 p.m., M De Simone via Jukebox-list wrote:
I’m currently working on a V200 amplifier and can’t figure out where the current draw is coming from. I’ve isolated it to the 6.3 heater circuit but can’t find any issue with it. The only problem is the humidity adjustment is missing the wire wound section so it’s basically not doing anything. I put 2 resistors in place as a replacement but when I fire up the amp my amp meter starts rising and I shut it down between 2 and 3 amps. Usually when texting one of these amplifiers it slowly rises to about 1.5 amps and holds steady there. What am I missing here?
Start by unplugging all the tubes and see what happens. Then plug half of them in and see if the current is OK...then 1/2 of the remaining tubes...splitting problems in half speeds up the discovery process I find.
John :-#)#
-- John's Jukes Ltd. 7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 Call (604)872-5757 (Pinballs, Jukes, Video Games) flippers.com "Old pinballers never die, they just flip out"
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On 2024/03/06 5:58 p.m., M De Simone wrote:
Hey John, thanks for the response. I’ve tested all the tubes and inserted voltage on the heater line with all tubes removed and it was better but as soon as I start putting in the tubes the current starts drawing more than usual. I still keep thinking back to the hum control pot. Can this affect the current draw if it’s missing? I also believe the output transformer needs to be replaced as resistance readings across the plates of the output tubes and centre tap of transformer differs by about 50%. I don’t think this would affect the heater circuit? Any help appreciated, Mauro
Hi Mauro, As Jay asks - why are you saying it is a heater issue? I too think the problem is more likely something in the B+ circuit and from your description of the output transformer variance in resistance would recommend that before going any further, that you isolate the output transformer by disconnecting its centre tap from the B+ circuit, then see if your current is spiking and leave the 6L6s unplugged. If your current is now normal, start looking for a replacement output transformer. John :-#)#
Sent from my iPhone
On Mar 6, 2024, at 8:36 PM, John Robertson via Jukebox-list <jukebox-list@lists.netlojix.com> wrote:
On 2024/03/06 4:57 p.m., M De Simone via Jukebox-list wrote:
I’m currently working on a V200 amplifier and can’t figure out where the current draw is coming from. I’ve isolated it to the 6.3 heater circuit but can’t find any issue with it. The only problem is the humidity adjustment is missing the wire wound section so it’s basically not doing anything. I put 2 resistors in place as a replacement but when I fire up the amp my amp meter starts rising and I shut it down between 2 and 3 amps. Usually when texting one of these amplifiers it slowly rises to about 1.5 amps and holds steady there. What am I missing here? Start by unplugging all the tubes and see what happens. Then plug half of them in and see if the current is OK...then 1/2 of the remaining tubes...splitting problems in half speeds up the discovery process I find.
John :-#)#
-- John's Jukes Ltd. 7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 Call (604)872-5757 (Pinballs, Jukes, Video Games) flippers.com "Old pinballers never die, they just flip out"
_______________________________________________ Jukebox-list mailing list -- jukebox-list@lists.netlojix.com To unsubscribe send an email to jukebox-list-leave@lists.netlojix.com %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s Searchable Archives: http://jukebox.markmail.org/
-- John's Jukes Ltd. 7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 Call (604)872-5757 (Pinballs, Jukes, Video Games) flippers.com "Old pinballers never die, they just flip out"
[snipped for brevity] On 3/6/2024 8:58 PM, M De Simone via Jukebox-list wrote:
I also believe the output transformer needs to be replaced as resistance readings across the plates of the output tubes and centre tap of transformer differs by about 50%. I don’t think this would affect the heater circuit?
If the output transformer reads like you say, yes it's bad. And if the amp hasn't been properly rebuilt, you will burn up a new one in no time. That's why you don't even plug in an amp of that age until after it's been rebuilt. I think you are confused about the heater circuit since it "normally" draws more current than the power transformer. How are you testing current? Tony
On 3/6/24 16:57, M De Simone via Jukebox-list wrote:
I’m currently working on a V200 amplifier and can’t figure out where the current draw is coming from. I’ve isolated it to the 6.3 heater circuit but can’t find any issue with it.
The heater current should be 3.15 amps at 6.3 volts by adding the values of all of the tubes. This is fed from the selection receiver on two of the pins of the large 4-pin Jones plug, not the transformer on the amplifier itself.
The only problem is the humidity adjustment is missing the wire wound section so it’s basically not doing anything. I put 2 resistors in place as a replacement but when I fire up the amp my amp meter starts rising and I shut it down between 2 and 3 amps.
It's a hum adjustment, not humidity. It just sets the center tap ground on the heater circuit. You can leave it out in most cases. Original is 75 ohms but 100 ohms will be fine for a replacement. Should be rated for at least half a watt for a 100-ohm pot.
Usually when texting one of these amplifiers it slowly rises to about 1.5 amps and holds steady there. What am I missing here?
Where are you measuring this current? Overall for selection receiver and amplifier on the AC line? Has the amplifier been recapped? Does the current drop substantially if you pull the 5U4? Are the output tubes redplating? -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
This just came to me. If your fuse in the amp is blowing, it 's not the heaters. They get their 6.3 volt power from the selection receiver. Unless the fuse that blows is in the selection receiver? On 3/6/2024 7:57 PM, M De Simone via Jukebox-list wrote:
I’m currently working on a V200 amplifier and can’t figure out where the current draw is coming from. I’ve isolated it to the 6.3 heater circuit but can’t find any issue with it. The only problem is the humidity adjustment is missing the wire wound section so it’s basically not doing anything. I put 2 resistors in place as a replacement but when I fire up the amp my amp meter starts rising and I shut it down between 2 and 3 amps. Usually when texting one of these amplifiers it slowly rises to about 1.5 amps and holds steady there. What am I missing here?
Sent from my iPhone _______________________________________________ Jukebox-list mailing list --jukebox-list@lists.netlojix.com To unsubscribe send an email tojukebox-list-leave@lists.netlojix.com %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s Searchable Archives:http://jukebox.markmail.org/
I’ll explain how I came to suspect the heater circuit. After completely rebuilding the amplifier and testing all tubes, I plugged the amplifier in on my test setup which runs though an ammeter and during initial test the reading climbed much faster and higher than normal, so I quickly shut it down and started troubleshooting. First I injected 115 v to the power transformer through a variac (slowly) and tested 5v heater of 5U4 and high voltage was all good with hardly any current being drawn. Then I isolated the 6.3v by injecting that voltage to the tube heater circuit and this caused the ammeter needle movement to read close to 3 amps. I did disconnect the output transformer centre tap but the result was the same. Later tonight I’m going to repeat this test just to confirm the outcome as I tested many different scenarios and forget exactly the outcomes. Tested with and without tubes isolating the heater line only. I’d like to blame the output transformer but I don’t think that would affect the test I did. Probably a simple solution but I’m just not seeing it. Thanks for the suggestions so far! Sent from my iPhone
On Mar 7, 2024, at 8:25 AM, Tony Miklos via Jukebox-list <jukebox-list@lists.netlojix.com> wrote:
This just came to me. If your fuse in the amp is blowing, it 's not the heaters. They get their 6.3 volt power from the selection receiver. Unless the fuse that blows is in the selection receiver?
On 3/6/2024 7:57 PM, M De Simone via Jukebox-list wrote: I’m currently working on a V200 amplifier and can’t figure out where the current draw is coming from. I’ve isolated it to the 6.3 heater circuit but can’t find any issue with it. The only problem is the humidity adjustment is missing the wire wound section so it’s basically not doing anything. I put 2 resistors in place as a replacement but when I fire up the amp my amp meter starts rising and I shut it down between 2 and 3 amps. Usually when texting one of these amplifiers it slowly rises to about 1.5 amps and holds steady there. What am I missing here?
Sent from my iPhone _______________________________________________ Jukebox-list mailing list --jukebox-list@lists.netlojix.com To unsubscribe send an email tojukebox-list-leave@lists.netlojix.com %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s Searchable Archives:http://jukebox.markmail.org/
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On 2024/03/07 6:02 a.m., M De Simone via Jukebox-list wrote:
I’ll explain how I came to suspect the heater circuit. After completely rebuilding the amplifier and testing all tubes, I plugged the amplifier in on my test setup which runs though an ammeter and during initial test the reading climbed much faster and higher than normal, so I quickly shut it down and started troubleshooting. First I injected 115 v to the power transformer through a variac (slowly) and tested 5v heater of 5U4 and high voltage was all good with hardly any current being drawn. Then I isolated the 6.3v by injecting that voltage to the tube heater circuit and this caused the ammeter needle movement to read close to 3 amps. I did disconnect the output transformer centre tap but the result was the same. Later tonight I’m going to repeat this test just to confirm the outcome as I tested many different scenarios and forget exactly the outcomes. Tested with and without tubes isolating the heater line only. I’d like to blame the output transformer but I don’t think that would affect the test I did. Probably a simple solution but I’m just not seeing it. Thanks for the suggestions so far!
Make some notes on the tests performed as you do them... Disconnecting the center tap of the output transformer does not stop the current rise? Leave it disconnected and pull the 5U4, leaving the other tubes all plugged in. Does the current rise as the filaments warm up with the B+ off? If yes, then something on the 6.3V circuit, probably a tube with a heater to cathode short. Perhaps the cathode of one tube is accidentally shorted to ground? If not, then troubleshoot the B+ starting with the choke - it may have an internal short to ground. You did replace the electrolytics C7, C13, C6-x, and C43 in your amp rebuild? John :-#)#
Sent from my iPhone
On Mar 7, 2024, at 8:25 AM, Tony Miklos via Jukebox-list <jukebox-list@lists.netlojix.com> wrote:
This just came to me. If your fuse in the amp is blowing, it 's not the heaters. They get their 6.3 volt power from the selection receiver. Unless the fuse that blows is in the selection receiver?
On 3/6/2024 7:57 PM, M De Simone via Jukebox-list wrote: I’m currently working on a V200 amplifier and can’t figure out where the current draw is coming from. I’ve isolated it to the 6.3 heater circuit but can’t find any issue with it. The only problem is the humidity adjustment is missing the wire wound section so it’s basically not doing anything. I put 2 resistors in place as a replacement but when I fire up the amp my amp meter starts rising and I shut it down between 2 and 3 amps. Usually when texting one of these amplifiers it slowly rises to about 1.5 amps and holds steady there. What am I missing here?
Sent from my iPhone _______________________________________________ Jukebox-list mailing list --jukebox-list@lists.netlojix.com To unsubscribe send an email tojukebox-list-leave@lists.netlojix.com %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s Searchable Archives:http://jukebox.markmail.org/
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-- John's Jukes Ltd. 7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 Call (604)872-5757 (Pinballs, Jukes, Video Games) flippers.com "Old pinballers never die, they just flip out"
What was the original problem/symptoms and if it blew a fuse, which one did it blow? On 3/7/2024 9:02 AM, M De Simone via Jukebox-list wrote:
I’ll explain how I came to suspect the heater circuit. After completely rebuilding the amplifier and testing all tubes, I plugged the amplifier in on my test setup which runs though an ammeter and during initial test the reading climbed much faster and higher than normal, so I quickly shut it down and started troubleshooting. First I injected 115 v to the power transformer through a variac (slowly) and tested 5v heater of 5U4 and high voltage was all good with hardly any current being drawn. Then I isolated the 6.3v by injecting that voltage to the tube heater circuit and this caused the ammeter needle movement to read close to 3 amps. I did disconnect the output transformer centre tap but the result was the same. Later tonight I’m going to repeat this test just to confirm the outcome as I tested many different scenarios and forget exactly the outcomes. Tested with and without tubes isolating the heater line only. I’d like to blame the output transformer but I don’t think that would affect the test I did. Probably a simple solution but I’m just not seeing it. Thanks for the suggestions so far!
Sent from my iPhone
On Mar 7, 2024, at 8:25 AM, Tony Miklos via Jukebox-list<jukebox-list@lists.netlojix.com> wrote:
This just came to me. If your fuse in the amp is blowing, it 's not the heaters. They get their 6.3 volt power from the selection receiver. Unless the fuse that blows is in the selection receiver?
On 3/6/2024 7:57 PM, M De Simone via Jukebox-list wrote: I’m currently working on a V200 amplifier and can’t figure out where the current draw is coming from. I’ve isolated it to the 6.3 heater circuit but can’t find any issue with it. The only problem is the humidity adjustment is missing the wire wound section so it’s basically not doing anything. I put 2 resistors in place as a replacement but when I fire up the amp my amp meter starts rising and I shut it down between 2 and 3 amps. Usually when texting one of these amplifiers it slowly rises to about 1.5 amps and holds steady there. What am I missing here?
Sent from my iPhone _______________________________________________ Jukebox-list mailing list --jukebox-list@lists.netlojix.com To unsubscribe send an emailtojukebox-list-leave@lists.netlojix.com %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s Searchable Archives:http://jukebox.markmail.org/
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On 3/7/24 06:02, M De Simone via Jukebox-list wrote:
I’ll explain how I came to suspect the heater circuit. After completely rebuilding the amplifier and testing all tubes, I plugged the amplifier in on my test setup which runs though an ammeter and during initial test the reading climbed much faster and higher than normal, so I quickly shut it down and started troubleshooting. First I injected 115 v to the power transformer through a variac (slowly) and tested 5v heater of 5U4 and high voltage was all good with hardly any current being drawn. Then I isolated the 6.3v by injecting that voltage to the tube heater circuit and this caused the ammeter needle movement to read close to 3 amps. I did disconnect the output transformer centre tap but the result was the same. Later tonight I’m going to repeat this test just to confirm the outcome as I tested many different scenarios and forget exactly the outcomes. Tested with and without tubes isolating the heater line only.
Are you saying that the current rises to 3 amps drawn from the AC line when the tube heater pins are connected via the Jones plug, even with all of the tubes removed, or are you measuring the current with an ammeter on the 6.3 volt heater circuit itself? The heater current of all of the tubes added up is a little over 3 amps at 6.3 volts, but this will only add about 0.16 amps to the AC line current as it's stepped down by the transformer in the WSR. I suspect that the rise in current isn't due to the heater circuit, but instead from the high voltage pulling excessive current when the tubes are hot and conducting. With all of the tubes inserted except for the 5U4, is the current drawn from the AC line excessive? In this scenario can you see the filaments glowing in the tubes or are they dark? It indeed sounds like the output transformer is defective. With power off and the center tap disconnected, what is the resistance from the center tap of the transformer to chassis? It should be near infinite. I suspect that the output transformer has shorted turns and possibly a short to ground from the primary winding. -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
Just wanted to close this thread. Thank you Jay, John and Tony for helping me through this issue with your suggestions. Before going back and trying all testing again I decided to replace the output transformer as if it was shorting (and it was) I couldn’t really test it properly. I proceeded to put a new transformer in and that fixed the excessive current draw and the amplifier is playing beautifully. Thanks again! Mauro Sent from my iPhone
On Mar 7, 2024, at 5:13 PM, Jay Hennigan via Jukebox-list <jukebox-list@lists.netlojix.com> wrote:
On 3/7/24 06:02, M De Simone via Jukebox-list wrote:
I’ll explain how I came to suspect the heater circuit. After completely rebuilding the amplifier and testing all tubes, I plugged the amplifier in on my test setup which runs though an ammeter and during initial test the reading climbed much faster and higher than normal, so I quickly shut it down and started troubleshooting. First I injected 115 v to the power transformer through a variac (slowly) and tested 5v heater of 5U4 and high voltage was all good with hardly any current being drawn. Then I isolated the 6.3v by injecting that voltage to the tube heater circuit and this caused the ammeter needle movement to read close to 3 amps. I did disconnect the output transformer centre tap but the result was the same. Later tonight I’m going to repeat this test just to confirm the outcome as I tested many different scenarios and forget exactly the outcomes. Tested with and without tubes isolating the heater line only.
Are you saying that the current rises to 3 amps drawn from the AC line when the tube heater pins are connected via the Jones plug, even with all of the tubes removed, or are you measuring the current with an ammeter on the 6.3 volt heater circuit itself? The heater current of all of the tubes added up is a little over 3 amps at 6.3 volts, but this will only add about 0.16 amps to the AC line current as it's stepped down by the transformer in the WSR.
I suspect that the rise in current isn't due to the heater circuit, but instead from the high voltage pulling excessive current when the tubes are hot and conducting.
With all of the tubes inserted except for the 5U4, is the current drawn from the AC line excessive? In this scenario can you see the filaments glowing in the tubes or are they dark?
It indeed sounds like the output transformer is defective. With power off and the center tap disconnected, what is the resistance from the center tap of the transformer to chassis? It should be near infinite. I suspect that the output transformer has shorted turns and possibly a short to ground from the primary winding.
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
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Nothing better than a success story. 😀 On Sun, Mar 10, 2024 at 3:31 PM M De Simone via Jukebox-list < jukebox-list@lists.netlojix.com> wrote:
Just wanted to close this thread. Thank you Jay, John and Tony for helping me through this issue with your suggestions. Before going back and trying all testing again I decided to replace the output transformer as if it was shorting (and it was) I couldn’t really test it properly. I proceeded to put a new transformer in and that fixed the excessive current draw and the amplifier is playing beautifully. Thanks again! Mauro
Sent from my iPhone
On Mar 7, 2024, at 5:13 PM, Jay Hennigan via Jukebox-list < jukebox-list@lists.netlojix.com> wrote:
On 3/7/24 06:02, M De Simone via Jukebox-list wrote:
I’ll explain how I came to suspect the heater circuit. After completely rebuilding the amplifier and testing all tubes, I plugged the amplifier in on my test setup which runs though an ammeter and during initial test the reading climbed much faster and higher than normal, so I quickly shut it down and started troubleshooting. First I injected 115 v to the power transformer through a variac (slowly) and tested 5v heater of 5U4 and high voltage was all good with hardly any current being drawn. Then I isolated the 6.3v by injecting that voltage to the tube heater circuit and this caused the ammeter needle movement to read close to 3 amps. I did disconnect the output transformer centre tap but the result was the same. Later tonight I’m going to repeat this test just to confirm the outcome as I tested many different scenarios and forget exactly the outcomes. Tested with and without tubes isolating the heater line only.
Are you saying that the current rises to 3 amps drawn from the AC line when the tube heater pins are connected via the Jones plug, even with all of the tubes removed, or are you measuring the current with an ammeter on the 6.3 volt heater circuit itself? The heater current of all of the tubes added up is a little over 3 amps at 6.3 volts, but this will only add about 0.16 amps to the AC line current as it's stepped down by the transformer in the WSR.
I suspect that the rise in current isn't due to the heater circuit, but instead from the high voltage pulling excessive current when the tubes are hot and conducting.
With all of the tubes inserted except for the 5U4, is the current drawn from the AC line excessive? In this scenario can you see the filaments glowing in the tubes or are they dark?
It indeed sounds like the output transformer is defective. With power off and the center tap disconnected, what is the resistance from the center tap of the transformer to chassis? It should be near infinite. I suspect that the output transformer has shorted turns and possibly a short to ground from the primary winding.
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
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participants (5)
-
Jay Hennigan -
John Robertson -
Jukebox Repairman -
M De Simone -
Tony Miklos