ZMF Aegis Official Thread

[VolatileLiquid]

There is numbers identifying pins at the bottom of the 5691. By comparing your other tube, you should figure it.

So it turns out I can't sleep without getting to the bottom of this thinking I will blow up my beautiful amp. Yes, I was too green to realise this but the listing showed the image without a description of defect so I did not make the connection that one of the two tubes had the centre thing missing. The seller had 100% feedback on ebay and over 1900 sales so I didn't think the risks through.

About the numbers, thanks, but it turns out the tube with the missing centre also does not show the numbers like the other tube. The ebay listing didn't actually show the base when selling nor mentioned about missing numbers. This seemed intentional and I learned my lesson. So I technically had 1/8 chances of getting it right and on the second go of Russian roulette, the sound was fine.

Without the numbers, it's hard to tell which orientation is right for the tube with missing centre. By pure chance, I now know the labels facing the same way produced sound in both channels and of good quality so far. Is it safe to operate this then? Or can remainder 6/8 orientations I have not tried and not daring to try can actually produce sound resulting in two channels as well? Since I already know the 12 o'clock position left and 11 o'clock position right leads to no sound resulting on left channel (right tube only with centre notch = correct seating as reference).

Did I just waste money?

The seller only said this in their auction description:

For your consideration are two RCA 5691 Red Base Tubes from 1956 & 1957

These tubes were tested on a Hickok 539C where the minimum value is 1000gm and the reading for a new tube is 1530gm or better.

The tubes tested at 1750gm/1750gm & 1750gm/15 00gm

 

[L0rdGwyn]

It was for about 15-20 secs before I switched it off as one missing channel was not right. If both left and right channels are now producing sound properly, would that be the right orientation? Or tubes can still sound right but be in the incorrect position? About to hit the bed but I'll have a closer look tomorrow on the tube base and take some pictures. Looks like I just dodged a bullet.

It's probably fine, but yes, one channel was out as the tube was in the incorrect orientation. There is a notch in the tube socket and the tube base so that they can only go in in one orientation. However, in some tubes the notch gets worn out and it can then go in the socket in the incorrect orientation.

 

[betula]

So it turns out I can't sleep without getting to the bottom of this thinking I will blow up my beautiful amp. Yes, I was too green to realise this but the listing showed the image without a description of defect so I did not make the connection that one of the two tubes had the centre thing missing. The seller had 100% feedback on ebay and over 1900 sales so I didn't think the risks through.

About the numbers, thanks, but it turns out the tube with the missing centre also does not show the numbers like the other tube. The ebay listing didn't actually show the base when selling nor mentioned about missing numbers. This seemed intentional and I learned my lesson. So I technically had 1/8 chances of getting it right and on the second go of Russian roulette, the sound was fine.

Without the numbers, it's hard to tell which orientation is right for the tube with missing centre. By pure chance, I now know the labels facing the same way produced sound in both channels and of good quality so far. Is it safe to operate this then? Or can remainder 6/8 orientations I have not tried and not daring to try can actually produce sound resulting in two channels as well? Since I already know the 12 o'clock position left and 11 o'clock position right leads to no sound resulting on left channel (right tube only with centre notch = correct seating as reference).

Did I just waste money?

Well, it can be enough of a reason to return the tube(s) as this should have been pointed out in the description.
On some tubes some pins are missing (as not all 8 are necessary) which makes it easier to work out the correct orientation. With all 8 pins intact and the numbers worn off this is a russian roulette. I would return the tubes if I were you.

 

[OctavianH]

Did I just waste money?

The tube works most probably fine and you can see a mark of the guiding pin here:

 

[betula]

So it turns out I can't sleep without getting to the bottom of this thinking I will blow up my beautiful amp. Yes, I was too green to realise this but the listing showed the image without a description of defect so I did not make the connection that one of the two tubes had the centre thing missing. The seller had 100% feedback on ebay and over 1900 sales so I didn't think the risks through.

About the numbers, thanks, but it turns out the tube with the missing centre also does not show the numbers like the other tube. The ebay listing didn't actually show the base when selling nor mentioned about missing numbers. This seemed intentional and I learned my lesson. So I technically had 1/8 chances of getting it right and on the second go of Russian roulette, the sound was fine.

Without the numbers, it's hard to tell which orientation is right for the tube with missing centre. By pure chance, I now know the labels facing the same way produced sound in both channels and of good quality so far. Is it safe to operate this then? Or can remainder 6/8 orientations I have not tried and not daring to try can actually produce sound resulting in two channels as well? Since I already know the 12 o'clock position left and 11 o'clock position right leads to no sound resulting on left channel (right tube only with centre notch = correct seating as reference).

Did I just waste money?

The seller only said this in their auction description:

For your consideration are two RCA 5691 Red Base Tubes from 1956 & 1957

These tubes were tested on a Hickok 539C where the minimum value is 1000gm and the reading for a new tube is 1530gm or better.

The tubes tested at 1750gm/1750gm & 1750gm/15 00gm

If you can work out the correct orientation based on @OctavianH's hint, you could use something like this to make swapping easier next time.

 

[mattiastomas]

If you can work out the correct orientation based on @OctavianH's hint, you could use something like this to make swapping easier next time.

Alternatively take a sharpie and follow the line leading out from the notch and mark a line on the side of the base. That way when you put in the tube just line up the mark with the notch on the socket.

 

[Toonartist]

Alternatively take a sharpie and follow the line leading out from the notch and mark a line on the side of the base. That way when you put in the tube just line up the mark with the notch on the socket.

I've done something similar (red mark) but I put it on both tubes including the one that still had the guide pin so I could validate both red lines were in the same position.... just to satisfy my paranoia

 

[VolatileLiquid]

Thanks so much guys! The support is overwhelming.

So basically if i get the right orientation here, it should operate as a normal tube... Or are there other risks to consider here apart from usual wear and tear?

 

[betula]

Thanks so much guys! The support is overwhelming.

So basically if i get the right orientation here, it should operate as a normal tube... Or are there other risks to consider here apart from usual wear and tear?

As long as the orientation is correct, you are good to go as normal.

 

[VolatileLiquid]

As long as the orientation is correct, you are good to go as normal.

Cheers buddy. This reminds me of a video game resident evil puzzle (for those who played this) where missing a detail leads to face palm moment. Looks like everyone here figured out the pitfalls when venturing NOS.

Have a good night/morning folks.

 

[Toonartist]

Thanks so much guys! The support is overwhelming.

So basically if i get the right orientation here, it should operate as a normal tube... Or are there other risks to consider here apart from usual wear and tear?

It should operate as normal. The broken guide pin wouldn't impact on the rest of the tube... providing that the rest of the tube is good anyway.

As @OctavianH pointed out, the clue where the guide pin was is still there. Probably a good idea to also mark the PIN numbers back on the bottom of the tube as well by aligning it up with the good one... just in case.

I've learned that if a tube stops working, put out a question here before binning it.... it maybe possible to bring it back to life

 

[Wes S]

They are sounding as big as the look.

The Philips EL51 w/Dual Trough Getters is in the amp, and sounding pretty darn good so far. More to come after burn in. . .

 

[betula]

They are sounding as big as the look.



The Philips EL51 w/Dual Trough Getters is in the amp, and sounding pretty darn good so far. More to come after burn in. . .

Nice! I wonder how their detail and resolution compares to the EL50 red base solid plates.

 

[JTbbb]

They are sounding as big as the look.



The Philips EL51 w/Dual Trough Getters is in the amp, and sounding pretty darn good so far. More to come after burn in. . .

I’m not letting you get the upper hand!…I’m going to get me a pair of these…

 

[Wes S]

Nice! I wonder how their detail and resolution compares to the EL50 red base solid plates.

I don't have any EL50 solid plates, but I can already tell you the resolution and detail is very impressive and easily hangs with (actually just might best?) my EL50 Mesh Plates and all other tubes. I need more time to compare, but having already heard little nuances I have not noticed before, I can confidently say they have a high level of detail and resolve.

More to come. . .