Very correct Gerald. Even Dentron and Amp Supply used 2.5A and 3A diodes as
does Ameritron from the beginning with the AL-80 series with 1N5408's.
I do a fairly large SB-200/220 repair business and 6M conversions and they
are the only amps with perennial diode problems. The 600ma ratings are
marginal to start and when you toss in cap leakage and tube arcs its often
time for lots of smoke as well as transformer failures.
Carl
KM1H
----- Original Message -----
From: <TexasRF@aol.com>
To: <w7ry@inbox.com>; <4cx250b@muohio.edu>; <amps@contesting.com>
Sent: Sunday, March 27, 2011 9:00 AM
Subject: Re: [Amps] SB-200 power supply diodes
> Think about this again. The SB200/220 both use a voltage doubler capacitor
> filter hv supply. We know that peak currents in these type supplies can be
> five to ten times the average current.
>
> So, with a .6 to .7 ampere average, those diodes are taking a 3 to 6
> Ampere
> hit 60 times every second.
>
> For the miniscule added cost it makes a lot of sense to use 1N5408 diodes.
> Reaming the mounting holes for the larger lead size is a trivial effort.
>
> If 1N5408 diodes had been available when those amplifiers were designed
> no
> doubt they would have been used. Especially so when you consider the
> equalizing capacitors and resistors would not be needed. I would remove
> them now
> as the parts that are not there can't fail. Who knows what those resistor
> values might be after upwards of 50 years use?
>
> 73,
> Gerald K5GW
>
>
>
>
>
>
>
> In a message dated 3/26/2011 11:25:25 A.M. Central Daylight Time,
> w7ry@inbox.com writes:
>
> Agreed Jim! 3 amp diodes are an overkill on the SB-200 and SB-220.
>
> 73
> Jim W7RY
>
>
> --------------------------------------------------
> From: "Jim Garland" <4cx250b@muohio.edu>
> Sent: Saturday, March 26, 2011 6:24 AM
> To: <amps@contesting.com>
> Subject: Re: [Amps] SB-200 power supply diodes
>
>> Kathy,
>> I'd advise replacing the diode string in your SB-200 with 1N4007 diodes
>> instead of 1N5408. Not that there's anything wrong with the 1N5408, but
>> the
>> holes in the circuit board will have to be drilled out to make them fit.
>> The
>> 1N4007 will be a perfect fit, and with a 1A/1000V rating, will be more
>> than
>> adequate for an SB-200. You should probably also replace the elderly
>> electrolytics in the amplifier while you have it apart.
>> 73,
>> Jim W8ZR
>>
>>> From: Kathy Bookmiller <wb2aio@yahoo.com>
>>> Subject: [Amps] SB200 diodes
>>> To: amps@contesting.com
>>> Message-ID: <795630.36304.qm@web59714.mail.ac4.yahoo.com>
>>> Content-Type: text/plain; charset=iso-8859-1
>>>
>>> Thanks to everyone for their replies. I'm going to order them from
> Mouser
>> and replace them
>>> all as that is the consensus of the replies I received both on-list and
>> off. Did take a run over
>>> to my local RS store and they had some that were close to the 1n5408s
>>> in
>> spec, but only a 3
>>> pack of them, so will order them all from Mouser.? That seems to be the
>> norm for RS. It
>>> seems about every time I go in there for some parts, they'll have them
> in
>> those drawers in
>>> the back, but only one or none is inside the compartment.
>>> While waiting for them to show, maybe I'll finally get into my old
>>> NCL2000
>> that is loosing
>>> it's drive and has been sitting on the repair bench for a year:) That
>>> is
>> how I ended up buying
>>> the SB200 when it showed up on Craigslist here last summer, while
> waiting
>> for a new set of
>>> tubes to show up.
>>> So I'll spend the weekend looking for the odd band fill in the WPX
>>> contest
>> and checking the
>>> capacitors in the SB200 and cleaning off the board of the old diodes.
>>> 73,
>>> Kathy
>> *************
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 10.0.1204 / Virus Database: 1498/3529 - Release Date: 03/25/11
>>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|