[Amps] The amp blows Fuses
Kevin Adam
n9iww at live.com
Mon Jul 10 17:22:38 EDT 2017
Did unhook the high side of the tubes mine blows cause the tubes were bad
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Today's Topics:
1. Re: SB220 step start blows fuses (Gary Schafer)
2. Re: SB220 step start blows fuses (Gary Schafer)
3. Re: SB220 step start blows fuses - c'mon (Dave Hachadorian)
----------------------------------------------------------------------
Message: 1
Date: Mon, 10 Jul 2017 12:41:52 -0500
From: "Gary Schafer" <garyschafer at largeriver.net>
To: "'Joe'" <nss at mwt.net>, <amps at contesting.com>
Subject: Re: [Amps] SB220 step start blows fuses
Message-ID: <7312056F9EB840859E71C2BD2DF7E280 at garyPC>
Content-Type: text/plain; charset="us-ascii"
Well, yes you would need a bulb in each side of the 220 circuit or two bulbs
in series (rather than parallel) on one side,
assuming that the amp is not a 4 wire amp that also uses 120 volts.
If something in the amp shorts you would have 220 volts across a single bulb
and the bulb would burn out.
73
Gary K4FMX
> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Joe
> Sent: Monday, July 10, 2017 9:26 AM
> To: amps at contesting.com
> Subject: Re: [Amps] SB220 step start blows fuses
>
> If you were to use this light bulb current limiter safety thing, but on
> a 220 variac, I assume you would have to put a light into each leg true?
>
> Joe WB9SBD
> Sig
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
> On 7/10/2017 7:50 AM, donroden at hiwaay.net wrote:
> > Agree with Gary !!
> >
> > Make a tester out of a garage light with a 300 or 500 watt halogen
> > element.
> > ( or pair ) relatively inexpensive and I always need an extra light
> > when looking for things in my garage.
> >
> > Don W4DNR
> >
> >
> >
> > Quoting Gary Schafer <garyschafer at largeriver.net>:
> >
> >> You don't have a big enough bulb.
> >>
> >> I use two 300 watt bulbs in parallel. 300 watt bulbs are about the
> >> largest
> >> you can find easily.
> >>
> >> I made up the bulb unit using a square electrical box and mounted two
> >> outdoor light sockets on it, an outlet and a regular house switch to
> >> short
> >> out the bulbs when I want to bypass the series bulbs.
> >> It works great for checking amps. It is really nice if you have an
> >> intermittent arc or want to let suspect capacitors cook for awhile
> >> with the
> >> amp is in standby as no harm is done if something arcs, the bulbs
> >> just light
> >> up bright.
> >>
> >> I sometimes plug the light bulb setup into a variac too.
> >>
> >> 73
> >>
> >> Gary K4FMX
> >>
> >>> -----Original Message-----
> >>> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Warren
> >>> Volz
> >>> Sent: Sunday, July 09, 2017 9:53 PM
> >>> To: amps; gudguyham at aol.com
> >>> Subject: Re: [Amps] SB220 step start blows fuses
> >>>
> >>> I may shortly be looking to purchase a variac.
> >>>
> >>> After building a dim bulb tester this weekend I have a minor update.
> >>>
> >>> With 120V connected, the HV primary disconnected and one tube in a
> >>> socket (doesn't matter which I use) the 100W bulb in my tester
> >>> lights up
> >>> bright. No fan and the meter lights aren't on. If I take out the
> tube
> >>> the fan and meter lights work. So I guess I have a shorted tube?
> Would
> >>> it be good to double check the DC/AC voltage on the filament supply
> >>> with
> >>> the tubes plugged in? That would show any sags that might exist.
> >>>
> >>> -Warren
> >>>
> >>> > On Jul 7, 2017, at 12:58 PM, gudguyham--- via Amps
> >>> <amps at contesting.com> wrote:
> >>> >
> >>> > I know I sound like a broken record but yes, a Variac is the way
> to
> >>> go. Especially with amps that can have power supply problems and
> gassy
> >>> tubes. You will hear the plate transformer groan and won't see HV
> >>> climbing on the meter if there is a problem in the PS long before
> the
> >>> smoke Genie appears. My Variac gets used daily several times after
> >>> doing ANY work on an amp. It's saved me loads of time fixing blown
> >>> parts that would normally occur if I had just turned an amp on with
> >>> problems. Best investment I ever made. 0-250 volts at 20 amps.
> >>> >
> >>> > Sent from AOL Mobile Mail
> >>> >
> >>> >
> >>> > -----Original Message-----
> >>> > From: Bill Turner <dezrat at outlook.com>
> >>> > To: Amps group <amps at contesting.com>
> >>> > Sent: Fri, Jul 7, 2017 12:34 PM
> >>> > Subject: Re: [Amps] SB220 step start blows fuses
> >>> >
> >>> >
> >>> > ------------ ORIGINAL MESSAGE ------------(may be snipped)
> >>> >
> >>> > On Fri, 7 Jul 2017 10:21:36 -0400, Mark B. wrote:
> >>> >
> >>> >> A variac varies voltage. It is not designed to limit current.
> >>> >
> >>> > REPLY:
> >>> >
> >>> > At the very low end of its range, a Variac limits current just
> >>> fine. I
> >>> > worked as a calibration technician at Tektronix for years, taking
> >>> > brand new scopes off the assembly line and powering them up for
> the
> >>> > first time. Believe me, a Variac is the only way to go with a unit
> >>> > which could have any number of problems at first. Over the years I
> >>> > powered up literally thousands of scopes this way and never a
> problem
> >>> > with current limiting.
> >>> >
> >>> > 73, Bill W6WRT
> >>> > _______________________________________________
> >>> > Amps mailing list
> >>> > <a href="mailto:Amps at contesting.com">Amps at contesting.com</a>
> >>> > <a href="http://lists.contesting.com/mailman/listinfo/amps"
> >>>
> target="_blank">http://lists.contesting.com/mailman/listinfo/amps</a>
> >>> > _______________________________________________
> >>> > Amps mailing list
> >>> > Amps at contesting.com
> >>> > http://lists.contesting.com/mailman/listinfo/amps
> >>>
> >>> _______________________________________________
> >>> Amps mailing list
> >>> Amps at contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/amps
> >>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps at contesting.com
> >> http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> >
> > DonR
> > _______________________________________________
> > Amps mailing list
> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> >
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
------------------------------
Message: 2
Date: Mon, 10 Jul 2017 12:46:52 -0500
From: "Gary Schafer" <garyschafer at largeriver.net>
To: "'Jim Garland'" <4cx250b at miamioh.edu>, <gudguyham at aol.com>,
<warren at warrenvolz.com>, <amps at contesting.com>
Subject: Re: [Amps] SB220 step start blows fuses
Message-ID: <DC6FB6D2BF4E4E13B5B9C37BB0B181D4 at garyPC>
Content-Type: text/plain; charset="us-ascii"
That's a lot of fuses.
73
Gary K4FMX
> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Jim Garland
> Sent: Monday, July 10, 2017 9:11 AM
> To: gudguyham at aol.com; warren at warrenvolz.com; amps at contesting.com
> Subject: Re: [Amps] SB220 step start blows fuses
>
> I've been reading this thread for some time, and while I agree with many
> of the suggestions (i.e., light bulb testers, variacs), I don't believe
> any of these are necessary to diagnose this fault. The SB220 is a
> straightforward, simple amplifier, and catastrophic faults that blow
> fuses aren't normally hard to diagnose, even without any test equipment.
> Looking at the schematic, here's what I would do.
>
> 1. Disconnect the red secondary plate transformer wire. Turn on the amp
> and see if the fan operates, the tubes light up, and that no fuses blow.
> If all looks good, that rules out a plate xfmr problem (keep your
> fingers crossed) and a filament xfmr problem (ditto), but leaves the
> possibility of a problem in the HV filter bank or an HV short in the
> tubes. If the fuse still blows, that means the plate xfmr is shorted, or
> that there's a short in the filament xfmr, or that a tube filament is
> shorted.
>
> 2. If the fuse still blows in step (1), then pull the tubes, leave the
> red HV secondary wire disconnected, and repeat the test. If now the fuse
> doesn't blow, then that rules out a short in either the plate
> transformer or filament transformer and points the problem to a filament
> short in a tube. If a fuse still blows with the tubes pulled, then we
> still have to suspect the filament xfmr or plate xfmr.
>
> 3 If the fuse still blows in step (2) (with the tubes unplugged), then
> you have little choice but to separately disconnect a primary wire from
> the plate xfmr and filament xfmr to see which one is bad. If the fuse
> only blows with the tubes plugged in, but doesn't blow with the tubes
> unplugged, (with the HV secondary wire disconnected) we know that the
> problem is a shorted tube filament.
>
> The most likely scenario is that the tubes will light and that the fan
> will work with the red plate xfmr secondary wire disconnected. If that's
> the case, then you need to pin down whether the problem is an HV short
> in a tube or a problem in the HV filter circuit. The easiest thing to do
> is to pull the plate caps off the tubes and hook back up the red
> secondary wire. If you turn on the amp and no fuses blow and the HV
> meter shows plate voltage, then you've got at least one bad tube. If the
> fuse blows with the plate caps disconnected, then you've got an HV
> filter problem. Look for shorted diodes in the rectifier bank. You may
> also have bad filter caps, but they're probably just open and not
> shorted. If this were my amp, I replace all the filter caps and diodes
> with modern components, just as a precautionary measure. That will
> probably fix your problem.
>
> 73,
> Jim W8ZR
>
>
> On 7/10/2017 3:08 AM, gudguyham--- via Amps wrote:
> > If you have no HV on the tube all you are doing is lighting the
> filament unless you have a HARD short that would be detectable with an
> ohm meter.
> > I am thinking that you have the fan hooked up wrong and somehow have
> the fan wired both into the plate transformer and filament transformer
> out of phase or something weird. If you have the fan wired correctly it
> should go on no matter what. It should have nothing to do with the tube
> being in the socket. Can I assume that before you embarked on this total
> rebuild you did that the amp worked OK? If it did, then you screwed up
> someplace when installing the mods. I am only hoping you did not burn
> up one of the transformers.
> >
> >
> > -----Original Message-----
> > From: Warren Volz <warren at warrenvolz.com>
> > To: amps <amps at contesting.com>; gudguyham <gudguyham at aol.com>
> > Cc: dezrat <dezrat at outlook.com>
> > Sent: Sun, Jul 9, 2017 10:52 pm
> > Subject: Re: [Amps] SB220 step start blows fuses
> >
> > I may shortly be looking to purchase a variac.
> >
> > After building a dim bulb tester this weekend I have a minor update.
> >
> > With 120V connected, the HV primary disconnected and one tube in a
> socket (doesn't matter which I use) the 100W bulb in my tester lights up
> bright. No fan and the meter lights aren't on. If I take out the tube
> the fan and meter lights work. So I guess I have a shorted tube? Would
> it be good to double check the DC/AC voltage on the filament supply with
> the tubes plugged in? That would show any sags that might exist.
> >
> > -Warren
> >
> >> On Jul 7, 2017, at 12:58 PM, gudguyham--- via Amps
> <amps at contesting.com> wrote:
> >>
> >> I know I sound like a broken record but yes, a Variac is the way to
> go. Especially with amps that can have power supply problems and gassy
> tubes. You will hear the plate transformer groan and won't see HV
> climbing on the meter if there is a problem in the PS long before the
> smoke Genie appears. My Variac gets used daily several times after
> doing ANY work on an amp. It's saved me loads of time fixing blown
> parts that would normally occur if I had just turned an amp on with
> problems. Best investment I ever made. 0-250 volts at 20 amps.
> >>
> >> Sent from AOL Mobile Mail
> >>
> >>
> >> -----Original Message-----
> >> From: Bill Turner <dezrat at outlook.com>
> >> To: Amps group <amps at contesting.com>
> >> Sent: Fri, Jul 7, 2017 12:34 PM
> >> Subject: Re: [Amps] SB220 step start blows fuses
> >>
> >>
> >> ------------ ORIGINAL MESSAGE ------------(may be snipped)
> >>
> >> On Fri, 7 Jul 2017 10:21:36 -0400, Mark B. wrote:
> >>
> >>> A variac varies voltage. It is not designed to limit current.
> >> REPLY:
> >>
> >> At the very low end of its range, a Variac limits current just fine.
> I
> >> worked as a calibration technician at Tektronix for years, taking
> >> brand new scopes off the assembly line and powering them up for the
> >> first time. Believe me, a Variac is the only way to go with a unit
> >> which could have any number of problems at first. Over the years I
> >> powered up literally thousands of scopes this way and never a problem
> >> with current limiting.
> >>
> >> 73, Bill W6WRT
> >> _______________________________________________
> >> Amps mailing list
> >> <a href="mailto:Amps at contesting.com">Amps at contesting.com</a>
> >> <a href="http://lists.contesting.com/mailman/listinfo/amps"
> target="_blank">http://lists.contesting.com/mailman/listinfo/amps</a>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps at contesting.com
> >> http://lists.contesting.com/mailman/listinfo/amps
> >
> > _______________________________________________
> > Amps mailing list
> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
------------------------------
Message: 3
Date: Mon, 10 Jul 2017 13:02:31 -0700
From: "Dave Hachadorian" <k6ll.dave at gmail.com>
To: <amps at contesting.com>
Subject: Re: [Amps] SB220 step start blows fuses - c'mon
Message-ID: <3C315C02701D49D193860476D6AAFFCB at Toshiba>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=response
C'mon guys, this is only an SB-220. It's a barebones amplifier
with no complicated protective circuits. It's easy to work on,
since it was built as a kit.
To troubleshoot this amp, you should need only one spare fuse.
Somewhere in the procedure below, the fuse will blow, and you
will know where the problem is.
First, remove the surge limiter circuit. It is a troublesome,
unnecessary item. Restore to factory configuration.
Disconnect the primaries of the plate and fil/bias transformer
and see if the fuse blows.
Connect the primary of the fil/bias transformer, with secondaries
disconnected, see if the fuse blows.
Connect the bias secondary of the fil/bias transformer and see if
the fuse blows.
Connect the filament secondary of the fil/bias transformer, with
the tubes removed. See if the fuse blows.
Plug in the tubes. See if the fuse blows.
Connect the primary of the plate transformer with secondary
disconnected, see if the fuse blows.
Connect the secondary of the plate transformer, with the B+ line
to the tubes disconnected. See if the tube blows.
Connect the b+ line to the tubes and see if the fuse blows.
It's a lot more fun to work on Tetrode amps with all kinds of
digital and analog protective circuitry!
Dave Hachadorian, K6LL
Big Bear Lake, CA
-----Original Message-----
From: donroden at hiwaay.net
Sent: Monday, July 10, 2017 5:50 AM
To: amps at contesting.com
Subject: Re: [Amps] SB220 step start blows fuses
Agree with Gary !!
Make a tester out of a garage light with a 300 or 500 watt
halogen element.
( or pair ) relatively inexpensive and I always need an extra
light
when looking for things in my garage.
Don W4DNR
Quoting Gary Schafer <garyschafer at largeriver.net>:
> You don't have a big enough bulb.
>
> I use two 300 watt bulbs in parallel. 300 watt bulbs are about
> the largest
> you can find easily.
>
> I made up the bulb unit using a square electrical box and
> mounted two
> outdoor light sockets on it, an outlet and a regular house
> switch to short
> out the bulbs when I want to bypass the series bulbs.
> It works great for checking amps. It is really nice if you have
> an
> intermittent arc or want to let suspect capacitors cook for
> awhile with the
> amp is in standby as no harm is done if something arcs, the
> bulbs just light
> up bright.
>
> I sometimes plug the light bulb setup into a variac too.
>
> 73
>
> Gary K4FMX
>
>> -----Original Message-----
>> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of
>> Warren Volz
>> Sent: Sunday, July 09, 2017 9:53 PM
>> To: amps; gudguyham at aol.com
>> Subject: Re: [Amps] SB220 step start blows fuses
>>
>> I may shortly be looking to purchase a variac.
>>
>> After building a dim bulb tester this weekend I have a minor
>> update.
>>
>> With 120V connected, the HV primary disconnected and one tube
>> in a
>> socket (doesn't matter which I use) the 100W bulb in my tester
>> lights up
>> bright. No fan and the meter lights aren't on. If I take out
>> the tube
>> the fan and meter lights work. So I guess I have a shorted
>> tube? Would
>> it be good to double check the DC/AC voltage on the filament
>> supply with
>> the tubes plugged in? That would show any sags that might
>> exist.
>>
>> -Warren
>>
>> > On Jul 7, 2017, at 12:58 PM, gudguyham--- via Amps
>> <amps at contesting.com> wrote:
>> >
>> > I know I sound like a broken record but yes, a Variac is the
>> > way to
>> go. Especially with amps that can have power supply problems
>> and gassy
>> tubes. You will hear the plate transformer groan and won't
>> see HV
>> climbing on the meter if there is a problem in the PS long
>> before the
>> smoke Genie appears. My Variac gets used daily several times
>> after
>> doing ANY work on an amp. It's saved me loads of time fixing
>> blown
>> parts that would normally occur if I had just turned an amp on
>> with
>> problems. Best investment I ever made. 0-250 volts at 20
>> amps.
>> >
>> > Sent from AOL Mobile Mail
>> >
>> >
>> > -----Original Message-----
>> > From: Bill Turner <dezrat at outlook.com>
>> > To: Amps group <amps at contesting.com>
>> > Sent: Fri, Jul 7, 2017 12:34 PM
>> > Subject: Re: [Amps] SB220 step start blows fuses
>> >
>> >
>> > ------------ ORIGINAL MESSAGE ------------(may be snipped)
>> >
>> > On Fri, 7 Jul 2017 10:21:36 -0400, Mark B. wrote:
>> >
>> >> A variac varies voltage. It is not designed to limit
>> >> current.
>> >
>> > REPLY:
>> >
>> > At the very low end of its range, a Variac limits current
>> > just fine. I
>> > worked as a calibration technician at Tektronix for years,
>> > taking
>> > brand new scopes off the assembly line and powering them up
>> > for the
>> > first time. Believe me, a Variac is the only way to go with
>> > a unit
>> > which could have any number of problems at first. Over the
>> > years I
>> > powered up literally thousands of scopes this way and never
>> > a problem
>> > with current limiting.
>> >
>> > 73, Bill W6WRT
>> > _______________________________________________
>> > Amps mailing list
>> > <a href="mailto:Amps at contesting.com">Amps at contesting.com</a>
>> > <a href="http://lists.contesting.com/mailman/listinfo/amps"
>> target="_blank">http://lists.contesting.com/mailman/listinfo/amps</a>
>> > _______________________________________________
>> > Amps mailing list
>> > Amps at contesting.com
>> > http://lists.contesting.com/mailman/listinfo/amps
>>
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
DonR
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