[R-390] R-390A Antenna matching, 26Z5W, 3TF7, 0A2 replacements available? Recommendations?

[Don R]

I just checked and VTI has NOS 25Z5 rectifier tubes for $3.90
https://vacuumtubesinc.com/index.php/25z5.html

3TF7 is $37.50
https://vacuumtubesinc.com/index.php/3tf7.html

0A2 is $5.50
https://vacuumtubesinc.com/index.php/catalogsearch/result/?q=0A2%2F150C2

Don Resor
hammondorganservice.com



Sent from someone's iPhone

> On Aug 11, 2019, at 9:45 PM, James Anderson <ScottA0227 at outlook.com> wrote:
> 
> Thank you for your help.
> 
> Scott Anderson
> IEC-USA
> 503-789-3438
> 
> On Aug 11, 2019, at 6:01 PM, Larry H <larry41gm at gmail.com<mailto:larry41gm at gmail.com>> wrote:
> 
> Hi Scott,  You can contact them directly at: sigmapert 'at' gmx 'dot' de and I believe they still produce some of those items.
> 
> However, unless your 120 vac power fluctuates, a 3tf7 is not necessary.  I suggest using a 12bh7 or 12by7, instead.  There's been discussions about this you can look up (search the archives with the HHI email reflector search tool).
> 
> And, as for the antenna balun, if you are not experiencing common mode interference, the balun signal loss is something to consider on weak signal reception.  The 125 ohm balanced antenna connection on these receivers is designed to work with impedances of 50 to 200 ohms without much of a mismatch. The loss is extremely small, so using a balun to overcome the imbalance would introduce more loss than without a balun.  The least insertion loss available today in this type of balun would be about .5 db on the low frequency side, and up to 2.5 db on the high side.  The maximum loss without a balun due to a mismatch on an R390A is about .3 db.  Impedance matching in this range on a receiver is not very important.
> 
> Regards, Larry
> 
> On Sun, Aug 11, 2019 at 11:21 AM James Anderson <ScottA0227 at outlook.com<mailto:ScottA0227 at outlook.com>> wrote:
> Do you know if Sigmaperts replacement as follows are still available?
> 
> 
>  1.  BNC 50 ohm unbalanced to Twinax 125 ohm balanced antenna adapter for the R-390A
>  2.  26Z5W replacement
>  3.  3TF7 replacement
>  4.  0A2 replacement
> 
> I am looking to update my R-390A and from a couple of recommendation you made of them I would like to buy them.
> If not available do you have suggestions for substitutes?
> 
> Thanks for your help,
> 
> J. Scott Anderson
> 503-789-3438
> 
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