[Moon-Net] 3CX1500A7 (8877) or 3CPX1500A7 ?

Edward R Cole kl7uw at acsalaska.net
Tue Nov 22 18:21:37 CET 2016


I built my 8877 back in 2008-2010 and here is a 
picture of some of the components before 
assembly.  I think the socket is the original 
EIMAC.  I didn't spend more than about $10 at the time.
http://www.kl7uw.com/8877%20project.jpg

I had more "fun" redesigning the HVPS, started 
with a Swan HF amp (3-400z) PS that would run 
600w out, then a surplus CAI PS that ran about 
800w at 2900v.  Finally rebuild of the HVPS to 
4200v 1.5A got my current set up running easily 
1400w (actually had it up to 2000w on a test).  I 
bought three EIMAC-8877 pulls at a local hamfest 
(the seller was only asking $10/ea. so figured it 
was a long shot).  I sold one tube for $50, and 
have run the other since 2010 (third is still 
untested spare).  These tubes are tough!  I've 
run them into a shorted feedline (accidently) and 
they output 1800w until self-protect ckt tripped 
(I am using the GM3SEK Triode Board - well worth the cost).
http://www.kl7uw.com/2m-8877.htm

Not sure how much will apply to getting the 
3CPX1500A7 going.  My testing reads like a blog.

73, Ed - KL7UW
many eme'rs and VHF friends helped me in this 
project: special hat's off to K7CW who drove 
800mi to get my new HV xfmr and provided my 7.5kV filter cap.

At 07:12 AM 11/22/2016, Ted Hartson wrote:

>I have used the YU-209 
>see: 
><http://forums.qrz.com/index.php?threads/8877-3cx1500-yu-209-tubes.202153/>http://forums.qrz.com/index.php?threads/8877-3cx1500-yu-209-tubes.202153/ 
>and traded a big TV tube for several of these 
>they seem to be a 'hardened 8877'. My 
>understanding is these tubes are used in medical 
>MRI machines and are replaced at 100 hours 
>routinely. the $250 USD seems typical Ted WA8ULG
>
>On 11/22/2016 8:46 AM, <mailto:TexasRF at aol.com>TexasRF at aol.com wrote:
>>Both tubes will plug into the same 7 pin 
>>ceramic socket used by 813 and other tubes back 
>>60 years or more. You have to add grid grounding tabs but that is trivial.
>>
>>73,
>>Gerald K5GW
>>
>>
>>
>>In a message dated 11/22/2016 9:05:51 A.M. 
>>Central Standard Time, <mailto:nss at mwt.net>nss at mwt.net writes:
>>
>>
>>Has anyone homebrewed tube sockets?
>>
>>I mean WOW, the prices on some sockets, Wow!
>>
>>Joe WB9SBD
>>[]
>>
>>The Original Rolling Ball Clock
>>Idle Tyme
>>Idle-Tyme.com
>><http://www.idle-tyme.com/>http://www.idle-tyme.com
>>On 11/22/2016 8:47 AM, W1KSZ wrote:
>>>
>>>You can download the datasheets for each tube 
>>>and verify if any differences do exist.
>>>
>>>
>>>73, Dick, W1KSZ
>>>
>>>On 11/22/2016 7:38 AM, F5HRY wrote:
>>>>
>>>>Be also aware that the mechanical dimensions are not strictly similar.
>>>>
>>>>
>>>>
>>>>As fas as I remember (quite a long time since 
>>>>I finished my last amp), the anode
>>>>
>>>>heatsink is a bit higher for the 3CPX.
>>>>
>>>>
>>>>
>>>>73,
>>>>
>>>>Hervé F5HRY
>>>>
>>>>
>>>>
>>>>
>>>> > Message du 22/11/16 10:46
>>>> > De : "Martin Andrew" 
>>>> <mailto:martin.andrew at btinternet.com><martin.andrew at btinternet.com>
>>>> > A : <mailto:moon-net at mailman.pe1itr.com>moon-net at mailman.pe1itr.com
>>>> > Copie à :
>>>> > Objet : Re: [Moon-Net] 3CX1500A7 (8877) or 3CPX1500A7 ?
>>>> >
>>>> >
>>>>Thanks for the replies on this.
>>>>I was pretty certain the two tubes were 
>>>>interchangable with a few minor voltage
>>>>adjustments, but it is always better to ask 
>>>>than go blindly into something one is not 100% sure about.
>>>>
>>>>So in January I will be starting the search 
>>>>for a spare 3CPX1500A7 preferably with Europe.
>>>>
>>>>Again many thanks for the help and information..
>>>>
>>>>Martin, GM6VXB
>>>>----- Original Message -----
>>>>From: <mailto:martin.andrew at btinternet.com>Martin Andrew
>>>>To: <mailto:moon-net at mailman.pe1itr.com>moon-net at mailman.pe1itr.com
>>>>Sent: Monday, November 21, 2016 7:49 PM
>>>>Subject: [Moon-Net] 3CX1500A7 (8877) or 3CPX1500A7 ?
>>>>
>>>> >
>>>>Looking to get a spare tube as down to my 
>>>>last one now after a failure in the old HPA.
>>>>Heater failure yet again even with a good 
>>>>three stage heater 'step start' fitted.
>>>>
>>>>Been looking for a 3CX1500A7 (8877) but they 
>>>>seem to be getting pretty rare in the UK and also very expensive.
>>>>So also looking at the 3CPX1500A7 which 
>>>>except for Anode voltage seems pretty similar, and also much lower price.
>>>>I know that the EHT supply I have will not go 
>>>>to much above 3.5KV so wondering if the 
>>>>3CPX1500 is happy with a much lower anode voltage than the specified 10KV max.
>>>>
>>>>Before I look at ordering one (or should I 
>>>>stay with the 8877 ?) does anyone know if the 
>>>>3CPX is a 'near' direct replacement for the 3CX series tube ?.
>>>>Physical size is the same and looks like it will go easily to 200Mhz.
>>>>
>>>>Martin, GM6VXB
>>>>
>>>> >
>>>>
>>>>----------
>>>> >
>>>>
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73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag Business e-mail:
     dubususa at gmail.com 
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