Bridge Diode and Tube Halfwave combination?

[Mars Amp Repair]

Hey folks,
I ran across something I've not seen before (see attchd drawing). I'm guessing the whole reason for the diodes in this configuration is so this designer did not have to use a center-tapped power transformer, but you tell me if I'm way out there.
I've seen where diodes are added in series with a tube rectifier circuit for protection, but my old brain is struggling with this configuration. If you were to remove the tube, the circuit should work just fine as a diode configured bridge rectifier. Now if the diodes that go to ground were the only diodes in the circuit, I can see where they might provide a 'virtual' kind of ground for the full-wave tube config. It would basically be a bridge rectifier with 1/2 of it being a tube & the other half being diodes. I can only surmise you would do that if you didn't want to pay for a center-tapped xformer , but why even incorporate a tube?
With all 4 diodes in the circuit, it appears the tube would basically be shunted by the diodes that are across it. Wouldn't the tube then be rendered ineffective?
Someone out there has probably seen this before.
BTW, this amp is having issues with it intermittently blowing the 100ohm virtual filament resistors. The amp now has all new but the rectifier tube. The other tubes are 6SL7 and 6V6. It did already blow the filament of the new 6V6 when it blew the virtual filament ground resistors I had just replaced. I'm using 1/2watt fusible replacement resistors so they won't smoke out when they blow. I don't have a 6X5 to try, but I doubt it's bad as it tests good & is not susceptible to tapping.
I just have a weird feeling that it's something involved with this unusual rectifier set-up.
Any ideas? Thanx, Glen.
No schemo for this amp, but it's pretty straight forward for this complement of tubes.

[mozz]

6X5 are known to short out and blow the power transformer. Zenith radios were known for this. I think someone put those diodes in there and didn't take out the socket.

[Mars Amp Repair]

I was half expecting the handle to fall off the cab, when these screws kept coming and coming and ....well, you get the idea!
Also, pic of underside.
Thanx, Glen

[Mars Amp Repair]

6X5 are known to short out and blow the power transformer. Zenith radios were known for this. I think someone put those diodes in there and didn't take out the socket.

OK, but a fullwave rectifier needs a center-tap on the power transformer to function properly...So, the tube configuration by itself would not have been functional without a center-tap or those two diodes.
Right?

[Helmholtz]

OK, but a fullwave rectifier needs a center-tap on the power transformer to function properly...So, the tube configuration by itself would not have been functional without a center-tap or those two diodes.
Right?

You're right. The SS diodes are wired as bridge rectifier rendering the 6X5 useless. Circuit should work the same with the 6X5 pulled.
I guess the PT is a replacement and the original one had a CT and twice the end-to-end voltage.

[mozz]

You can see the dremel marks where the power transformer area was cut. Looks like a Danelectro made unit? Maybe a homemade chassis?

[Mars Amp Repair]

Yes, this is a 'Boutique' amp manufactured by some dude in Spokane, WA. The chassis is basically a stock box that has been cut out to fit the various components. For various reasons; witness marks, undisturbed soldering, I believe this amp is all original.
Still, I don't see any comments on how this halfwave rectifier setup could possibly work with a non-center tapped transformer with none of the diodes added. I never want to disparage anyone esp without sufficient information, but I beginning to think the builder only had non-center tapped transformers & was searching for a means to make it work. I may, for the hell of it, remove the two diodes that parallel the 6X5, and just see how it works.
I'm am still faced with why it intermittently blows the filament virtual ground resistors and in once instance, blew the 6V6 filament.
Perhaps I'll reach out to John Mergili.
I once reached out the the owner of Divided by 13 amps and found him to be super helpful.
Ya never know! g

[mozz]

I've bought at least a half dozen cabinets from him, excellent work. Check those 4 diodes for open and shorts. Like i said, the 6X5 is know to short out H-K. Good read here about floating the filaments. Besure the tube is GT, not plain 6x5. Anyway, i would take that socket out of there. What is the B+?
https://antiqueradios.com/forums/viewtopic.php?t=193858

[Mars Amp Repair]

I've bought at least a half dozen cabinets from him, excellent work. Check those 4 diodes for open and shorts. Like i said, the 6X5 is know to short out H-K. Good read here about floating the filaments. Besure the tube is GT, not plain 6x5. Anyway, i would take that socket out of there. What is the B+?
https://antiqueradios.com/forums/viewtopic.php?t=193858

Thanx, mozz.
That link takes me to an article about the 6X5 propensity to short, but nothing about virtual floating filaments. I'm pretty familiar with the issue as well as DC offsetting the filament to deal with the noise level.
I sent a message to John Mergili via his website. I'll follow up once I hear from him, or resolve the issue.

[mozz]

I have seen those 100 ohm resistors burn up before, someone here can tell you why, I think because of a shorted tube. I asked about the B+ due to the 6x5 not being able to handle high voltage and is limited to 70ma current.

[Helmholtz]

The 6X5 would take out the heater balancing resistors when arcing between heater and cathode.
Floating the heaters would require an extra heater winding for the 6X5.
I would either remove the 6X5 or at least dicsconnect the cathode.
The tube is a cheater here anyway as it doesn't carry current.

To add, removing the 2 diodes across the 6X5 would significantly lower B+ and thus power output.

[J M Fahey]

That tube rectifier does nothing useful or at all and *may* become a problem, because it will pass no current but still stand peak voltage relative to ground.

[Mars Amp Repair]

That tube rectifier does nothing useful or at all and *may* become a problem, because it will pass no current but still stand peak voltage relative to ground.

Thanx all.
I emailed with the maker of this amp, John Mergeli, and got the scoop on what is up with this particular 'specimen'. I'll fill you all in once I get his approval to post it here. Glen

[Mars Amp Repair]

So, here's the story about this amp.
According to John Mergili, who btw is a very amiable guy, stopped making amps in 2018 and focused on making cabs. 'Mozz' in a comment above, says he has purchased many cabs from Mergili & they're excellent. I've looked at his site & I have to agree they are very cool.
Anyway, John had a bunch of parts left over from making amps and would just cobble an amp together from what he had left just for fun and never intended them to be sold. He gave one to a buddy who turned around and sold it to a Pawn Shop. This current owner purchased it from there.
Bottom line is it is not representative of the amps he designed & sold on the open market.
SO, turns out he just put the rectifier tube in there to look cool, but not to be a functionable element. That threw me & us for a minute.
I will say that were it not for the 6X5 shorting, this amp would still be working and have a happy customer, who now can be happy again.
It was interesting to put the two stories together and follow the path of this amp from inception to final purchase.
glen