[Amps] Alpha 91b problem
Rodrigo
ct1bxt at gmail.com
Sun Nov 20 14:24:05 EST 2022
Hi,
I solve a problem on ACOM 1500 witch had a leek between hi voltage and
filament that blow fuses as soon as I connect the ground to chassis .
The solution was a new transformer, 600 euro !!!
This new amplifiers are so less space that is almost impossible to put
one more transformer inside.
Best 73
Rodrigo
ct1bxt
Às 18:51 de 20/11/2022, amps-request at contesting.com escreveu:
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> Today's Topics:
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> 1. Re: Alpha 91b problem (Terry Baxter)
> 2. Re: Alpha 91b problem (gudguyham at aol.com)
> 3. Re: Alpha 91b problem (bmm57)
>
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 20 Nov 2022 17:54:36 +0000
> From: "Terry Baxter" <w6cbureau at san.rr.com>
> To: "'K9FD'" <merv.k9fd at gmail.com>, "'amps at contesting.com'"
> <amps at contesting.com>
> Subject: Re: [Amps] Alpha 91b problem
> Message-ID: <c84bd496fbbaf3f966e9378eef0abb5c5e494cd3 at webmail>
> Content-Type: text/plain; charset=UTF-8
>
> Another much cheaper alternative is to just use a separate bias or
> screen supply depending on which one has failed. However since my
> transformer has a 4.6k ohm short from the 105 V winding to the HV
> winding what would be the results of this short? Would floating the
> bad bias winding have an effect on the HV winding? Would the HV
> winding be compromised with this short? Someone out there would have
> the answer to that.
>
> Terry/N6CW
>
> -----------------------------------------From: "K9FD"
> To: amps at contesting.com
> Cc:
> Sent: Sunday November 20 2022 11:34:19AM
> Subject: Re: [Amps] Alpha 91b problem
>
> I have a 91B that has the exact same symptoms, and it appears its the
> transformer.
> So you can add another to the list. Also have a 99 and it has just
> went south,
> hoping its a shorted tube and not the tranny on that one.
> I would sure be in the market for a transformer if any one has one.
> Not
> sure I will
> spend 1000 for a new one to keep the 91 on the air.
> 73 Merv K9FD
> > I have a defective Alpha 91 transformer in my junk pile. WD8CCC?s
> amp started blowing primary fuses probably 8 to 10 years ago now. The
> problem was an internal winding to winding short. The transformer
> would make full AC voltage on the HV secondary, until the HV rectifier
> board was connected. I forget now, it has been so long ago, which
> winding was shorted internally to the HV winding.
> >
> > I had Ben order one from Alpha. They were kind of condescending
> about it; they did not believe it could be the problem. Finally they
> sold him one (they had a used one), while stressing they would accept
> a return when it didn?t fix the problem. I had the amp running
> already using an external HV winding. Apparently at the time it was
> not a commonly known issue. It was a new problem to me, but I only
> occasionally repair amps for friends so don?t see as many cases as
> folks who do this all the time.
> >
> > Sorry to hear 91B transformer failures are becoming more common.
> Ben?s amp is still going strong.
> >
> > 73 Charlie N8RR
> >
> >
> >
> > Sent from Mail [1] for Windows
> >
> > From: Alek Petkovic
> > Sent: Sunday, November 20, 2022 1:59 AM
> > To: amps at contesting.com
> > Subject: Re: [Amps] Alpha 91b problem
> >
> > Yes. I have a shot transformer from a 91B here. Similar problems to
> yours.
> >
> > The owner bit the bullet several years ago and bought the Hammond
> > replacement transformer and the hv/screen supply board. The amp has
> been
> > sold to another friend and it is in daily use. In other words, well
> > worth the cost.
> >
> > 73, Alek, VK6APK
> >
> > On 20/11/2022 8:38 am, Terry Baxter wrote:
> >>
> >> All,
> >>
> >> Recently I wrote about a problem I had with my Alpha 91b. It
> popped
> >> the rear panel fuse F3 (2 amp). The problem turned out to be a bad
> >> power transformer. In my case the secondary winding for the 105V
> power
> >> across pins 1&2 on connector J2. This should read approx 3 ohms.
> My
> >> transformer read 10K ohms. In addition it also read 4.5K ohms to
> the
> >> HV secondary winding pins 1&2 on J1. A good transformer should
> read 3
> >> ohms across pins 1&2 on J2. It should read 10 ohms across pins 4&5
> on
> >> J2 and less than 1 ohm across pins 6&7 and 7&8 on J2. I measured
> 500
> >> ohms across the high voltage secondary. Do this quickly as it can
> get
> >> interesting if you leave the ohmmeter on the primary. There should
> be
> >> a wide open reading between any pin on J2 to J1. There should be
> no
> >> resistance between any pin on J1 or J2 to the transformer body.
> All
> >> resistance readings are with all primary and secondary connections
> >> removed from the Power Supply board (in other words all connectors
> >> related to the power transformer). This quick check should confirm
> >> whether your transformer is good or bad.
> >>
> >> I had several responses asking for my findings on this issue. From
> >> what I learned a lot of the transformers in the 91b are failing. A
> new
> >> transformer from Hammond is currently selling for $1000 plus tax
> and
> >> shipping. I was fortunate to find a replacement transformer at a
> very
> >> affordable price.
> >>
> >> Sorry for the length of this note. I hope it will help answer any
> >> questions on this failure.
> >>
> >> Terry/N6CW
> >>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps at contesting.com
> >>
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> ------------------------------
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> Message: 2
> Date: Sun, 20 Nov 2022 18:26:40 +0000 (UTC)
> From: "gudguyham at aol.com" <gudguyham at aol.com>
> To: K9FD <merv.k9fd at gmail.com>, <amps at contesting.com>
> Subject: Re: [Amps] Alpha 91b problem
> Message-ID: <1477135217.1477646.1668968800800 at mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> I thought I heard that Acom might have replacement transformers for the 91b/99 amps. After all Acom built them. ?It?s very possible that the new Acom 2000a transformer can be retrofitted into the 91b or they might even have direct replacements. ?It?s worth an email to Val. ?The 200a is basically an updated 91b it uses the same tubes so all the voltages are there in that transformer. ?I?m pretty sure it?s $1000 but less. ?Worth a look see.
>
>
> Sent from the all new AOL app for iOS
>
>
> On Sunday, November 20, 2022, 11:34 AM, K9FD <merv.k9fd at gmail.com> wrote:
>
> I have a 91B that has the exact same symptoms,? and it appears its the
> transformer.
> So you can add another to the list.?? Also have a 99 and it has just
> went south,
> hoping its a shorted tube and not the tranny on that one.
> I would sure be in the market for a transformer if any one has one.? Not
> sure I will
> spend 1000 for a new one to keep the 91 on the air.
> 73 Merv K9FD
>> I have a defective Alpha 91 transformer in my junk pile.? WD8CCC?s amp started blowing primary fuses probably 8 to 10 years ago now.? The problem was an internal winding to winding short.? The transformer would make full AC voltage on the HV secondary, until the HV rectifier board was connected.? I forget now, it has been so long ago, which winding was shorted internally to the HV winding.
>>
>> I had Ben order one from Alpha.? They were kind of condescending about it; they did not believe it could be the problem.? Finally they sold him one (they had a used one), while stressing they would accept a return when it didn?t fix the problem.? I had the amp running already using an external HV winding.? Apparently at the time it was not a commonly known issue.? It was a new problem to me, but I only occasionally repair amps for friends so don?t see as many cases as folks who do this all the time.
>>
>> Sorry to hear 91B transformer failures are becoming more common.? Ben?s amp is still going strong.
>>
>> 73 Charlie N8RR
>>
>>
>>
>> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows
>>
>> From: Alek Petkovic<mailto:vk6apk at bigpond.com>
>> Sent: Sunday, November 20, 2022 1:59 AM
>> To: amps at contesting.com<mailto:amps at contesting.com>
>> Subject: Re: [Amps] Alpha 91b problem
>>
>> Yes. I have a shot transformer from a 91B here. Similar problems to yours.
>>
>> The owner bit the bullet several years ago and bought the Hammond
>> replacement transformer and the hv/screen supply board. The amp has been
>> sold to another friend and it is in daily use. In other words, well
>> worth the cost.
>>
>> 73, Alek, VK6APK
>>
>> On 20/11/2022 8:38 am, Terry Baxter wrote:
>>> ? ? ? ? All,
>>>
>>> ? ? ? ? Recently I wrote about a problem I had with my Alpha 91b. It popped
>>> the rear panel fuse F3 (2 amp). The problem turned out to be a bad
>>> power transformer. In my case the secondary winding for the 105V power
>>> across pins 1&2 on connector J2. This should read approx 3 ohms. My
>>> transformer read 10K ohms. In addition it also read 4.5K ohms to the
>>> HV secondary winding pins 1&2 on J1. A good transformer should read 3
>>> ohms across pins 1&2 on J2. It should read 10 ohms across pins 4&5 on
>>> J2 and less than 1 ohm across pins 6&7 and 7&8 on J2. I measured 500
>>> ohms across the high voltage secondary. Do this quickly as it can get
>>> interesting if you leave the ohmmeter on the primary. There should be
>>> a wide open reading between any pin on J2 to J1. There should be no
>>> resistance between any pin on J1 or J2 to the transformer body. All
>>> resistance readings are with all primary and secondary connections
>>> removed from the Power Supply board (in other words all connectors
>>> related to the power transformer). This quick check should confirm
>>> whether your transformer is good or bad.
>>>
>>> ? ? ? ? I had several responses asking for my findings on this issue. From
>>> what I learned a lot of the transformers in the 91b are failing. A new
>>> transformer from Hammond is currently selling for $1000 plus tax and
>>> shipping. I was fortunate to find a replacement transformer at a very
>>> affordable price.
>>>
>>> ? ? ? ? Sorry for the length of this note. I hope it will help answer any
>>> questions on this failure.
>>>
>>> ? ? ? ? Terry/N6CW
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.contesting.com%2Fmailman%2Flistinfo%2Famps&data=05%7C01%7C%7C1f667f0206ae46f1e38a08dacac4b7f2%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638045243558029621%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=0bTtfA6sCVnqEnGjD3MvtELHbOr6MIgLgZ%2BnIWh0PNw%3D&reserved=0
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> ------------------------------
>
> Message: 3
> Date: Sun, 20 Nov 2022 12:51:04 -0600
> From: bmm57 <bmm57 at sbcglobal.net>
> To: "gudguyham at aol.com" <gudguyham at aol.com>, K9FD
> <merv.k9fd at gmail.com>, amps at contesting.com
> Subject: Re: [Amps] Alpha 91b problem
> Message-ID: <1389215112.404365.1668970268872 at sbcglobal.net>
> Content-Type: text/plain; charset=utf-8
>
> Acom does not build a transformer replacement for alpha 91b or 99, Hamilton is the only one who has a replacement right nowFor $1000.00 plus shipping.?I have replaced over 20 Transformers in these 2 models in the last 6 years here at Array Solutions repair.Billy MacAK5DXSent via the Samsung Galaxy S9+, an AT&T 5G Evolution capable smartphone
> -------- Original message --------From: gudguyham--- via Amps <amps at contesting.com> Date: 11/20/22 12:26 PM (GMT-06:00) To: K9FD <merv.k9fd at gmail.com>, amps at contesting.com Subject: Re: [Amps] Alpha 91b problem I thought I heard that Acom might have replacement transformers for the 91b/99 amps. After all Acom built them. ?It?s very possible that the new Acom 2000a transformer can be retrofitted into the 91b or they might even have direct replacements. ?It?s worth an email to Val. ?The 200a is basically an updated 91b it uses the same tubes so all the voltages are there in that transformer. ?I?m pretty sure it?s $1000 but less. ?Worth a look see.Sent from the all new AOL app for iOSOn Sunday, November 20, 2022, 11:34 AM, K9FD <merv.k9fd at gmail.com> wrote:I have a 91B that has the exact same symptoms,? and it appears its the transformer.So you can add another to the list.?? Also have a 99 and it has just went south,hoping its a shorted tube and not the tranny on that one.I would sure b
> e in the market for a transformer if any one has one.? Not sure I willspend 1000 for a new one to keep the 91 on the air.73 Merv K9FD> I have a defective Alpha 91 transformer in my junk pile.? WD8CCC?s amp started blowing primary fuses probably 8 to 10 years ago now.? The problem was an internal winding to winding short.? The transformer would make full AC voltage on the HV secondary, until the HV rectifier board was connected.? I forget now, it has been so long ago, which winding was shorted internally to the HV winding.>> I had Ben order one from Alpha.? They were kind of condescending about it; they did not believe it could be the problem.? Finally they sold him one (they had a used one), while stressing they would accept a return when it didn?t fix the problem.? I had the amp running already using an external HV winding.? Apparently at the time it was not a commonly known issue.? It was a new problem to me, but I only occasionally repair amps for friends so don?t see as many cas
> es as folks who do this all the time.>> Sorry to hear 91B transformer failures are becoming more common.? Ben?s amp is still going strong.>> 73 Charlie N8RR>>>> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows>> From: Alek Petkovic<mailto:vk6apk at bigpond.com>> Sent: Sunday, November 20, 2022 1:59 AM> To: amps at contesting.com<mailto:amps at contesting.com>> Subject: Re: [Amps] Alpha 91b problem>> Yes. I have a shot transformer from a 91B here. Similar problems to yours.>> The owner bit the bullet several years ago and bought the Hammond> replacement transformer and the hv/screen supply board. The amp has been> sold to another friend and it is in daily use. In other words, well> worth the cost.>> 73, Alek, VK6APK>> On 20/11/2022 8:38 am, Terry Baxter wrote:>>>>? ? ? ? All,>>>>? ? ? ? Recently I wrote about a problem I had with my Alpha 91b. It popped>> the rear panel fuse F3 (2 amp). The problem turned out to be a bad>> power transformer. In my case the secondary
> winding for the 105V power>> across pins 1&2 on connector J2. This should read approx 3 ohms. My>> transformer read 10K ohms. In addition it also read 4.5K ohms to the>> HV secondary winding pins 1&2 on J1. A good transformer should read 3>> ohms across pins 1&2 on J2. It should read 10 ohms across pins 4&5 on>> J2 and less than 1 ohm across pins 6&7 and 7&8 on J2. I measured 500>> ohms across the high voltage secondary. Do this quickly as it can get>> interesting if you leave the ohmmeter on the primary. There should be>> a wide open reading between any pin on J2 to J1. There should be no>> resistance between any pin on J1 or J2 to the transformer body. All>> resistance readings are with all primary and secondary connections>> removed from the Power Supply board (in other words all connectors>> related to the power transformer). This quick check should confirm>> whether your transformer is good or bad.>>>>? ? ? ? I had several responses asking for my findings on this issue. From>>
> what I learned a lot of the transformers in the 91b are failing. A new>> transformer from Hammond is currently selling for $1000 plus tax and>> shipping. I was fortunate to find a replacement transformer at a very>> affordable price.>>>>? ? ? ? Sorry for the length of this note. I hope it will help answer any>> questions on this failure.>>>>? ? ? ? Terry/N6CW>>>> _______________________________________________>> Amps mailing list>> Amps at contesting.com>> https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.contesting.com%2Fmailman%2Flistinfo%2Famps&data=05%7C01%7C%7C1f667f0206ae46f1e38a08dacac4b7f2%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638045243558029621%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=0bTtfA6sCVnqEnGjD3MvtELHbOr6MIgLgZ%2BnIWh0PNw%3D&reserved=0> _______________________________________________> Amps mailing list> Amps at contesting.com> https://nam12.safelinks.protection.outlook.com/
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