Late 50' tube... who guess ! (The Ondioline)

[zamproject]

The OA2 is fed via a 100k resistor, so the current could never exceed a couple of mA.

In situ it was 4x39K 1W paralleled... I put a 10K 2W IIRC
The shemo is the initial release published in the late 40' early 50' which have some mistake or update since (considering my Ondioline second half of 50')

By the way, we talk about it few week ago in this topic, OA2 giving more than 160V, I replace it and regulation was fine since with 150V.

 

[abbey road d enfer]

In situ it was 4x39K 1W paralleled... I put a 10K 2W IIRC

OK. So, according to this, the current in the OA2 should be about 13mA.

 

[zamproject]

OK. So, according to this, the current in the OA2 should be about 13mA.

Yes as soon as everything is warmed up

With 2x275Vac the graph for 5Z4 gives a DC output of 325V, to which you substract 10 V in the choke, resulting in 315V for B+. This is for 80mA quiescent.
If it's actually a 5Y3, it has higher voltage drop than 5Z4, so it may be correct.

My math for the 550V (370FX) give about 300/305 for the 5Y3 @80mA (before choke)
with the 369HX (450V, your initial suggestion) I only have 250V, 240 after choke (@80mA) that's way too low for my need and there is the 370JX at 500V is just under too.

So I suppose I keep my initial choice and follow you with you later statement about the 370FX at 550Vac (390Vrms, loaded)

Best
Zam

 

[garp]

i have one like this waiting to be restored for years (

 

[zamproject]

i have one like this waiting to be restored for years (

That's some work ...

 

[zamproject]

Sound is back
Little low on B+ but I'll see.

"fun" (not so) of the day...I was enthusiastic to receive the new trafo... I pre-wire everything (before bolting the trafo, chassis need rework) including all CT, meaning 5V too
Hopefully I was monitoring with two DDM and the hand on the variac...

grill cloth over aperture is changed too, for "vintage gold" the old one have to many holes and scratches

soon the end !

Best
Zam

 

[boji]

 

[PermO]

Yeah that clip is just superb !

What an amazing instrument.

 

[zamproject]

Hey

The transformer is now mounted on lower chassis (need some metal rework...)
As already say I'm little low on B+, about 12/13V with 267V. it's around 5% so I think it's ok.

I already blow two fuse in two days, and do proper measurement, I have 320mA at pri (240V country) and the fuse was 400mA, that was my ultra safe margin which don't like much inrush when I don't use the variac, I'll update to 500 or 630mA and see (before putting higher value), I prefer to change fuses once or twice a year due to underrating fuse than blowing things in the Ondioline. (I'll probably add fuse at HT secondary too)
At HT the choke drop about 20V more than expected, and HT current is about 95mA for the whole machine wired
Power tube bias measures give a good match, 23.6 and 23.0 Ip, 6W each, and 2W for both at Ig2, tube are safe

Side question, can someone tell me what "Iex" mean at this datasheet
https://www.hammfg.com/files/parts/pdf/370FX.pdffirst line in the tab, I don't understand the condition, for only one primary winding used ?!? WHT-BLK
the trafo is given for 140VA, 132mA max don't make sense ? or is that what they put in for the measure ?

I'm back soon

Cheers
Zam

 

[abbey road d enfer]

Hey

The transformer is now mounted on lower chassis (need some metal rework...)
As already say I'm little low on B+, about 12/13V with 267V. it's around 5% so I think it's ok.

I already blow two fuse in two days, and do proper measurement, I have 320mA at pri (240V country) and the fuse was 400mA, that was my ultra safe margin which don't like much inrush when I don't use the variac, I'll update to 500 or 630mA and see (before putting higher value), I prefer to change fuses once or twice a year due to underrating fuse than blowing things in the Ondioline. (I'll probably add fuse at HT secondary too)
At HT the choke drop about 20V more than expected, and HT current is about 95mA for the whole machine wired

Usually fuses are rated at about 2x the nominal current. Have you used slow-blo fuses (T-type)?

Side question, can someone tell me what "Iex" mean at this datasheet
https://www.hammfg.com/files/parts/pdf/370FX.pdf

Iex is the EXcitation current, i.e. the minimum current the primary will draw even if there is no load. Typically, for calculations, you have to add this value to the reflected current of all the secondaries under load. 132mA is for each primary. When they are in series it's the only current, but when they are in parallels, the current is double.

 

[zamproject]

Hello Abby

Yes I use Temporized fuses, without respecting the x1.5 or x2 rules because most of power on since was with variac at each component change or rewiring, but recently as it's mostly finished and I'm more in the fine tuning of the whole thing I do hard power on. I just put a 500mA if it blow to fast I'll go for 630mA

Iex is the EXcitation current, i.e. the minimum current the primary will draw even if there is no load. Typically, for calculations, you have to add this value to the reflected current of all the secondaries under load. 132mA is for each primary. When they are in series it's the only current, but when they are in parallels, the current is double.

Tks for this clarification, so this is the trafo own loos

math seem to confirm well
2A@5V->42mA
[email protected]>105mA
95mA@560V-->41mA
adding 132mA give 320mA...what I measure despite some approximations

Cheers
Zam

 

[abbey road d enfer]

Tks for this clarification, so this is the trafo own loos

The magnetizing current is not entirely wasted as loss. It is in quadrature with the voltage, so the actual power is small, but due to the high distortion and the Joule and iron core losses, it is not unsignificant.

 

[zamproject]

Time fly...

Since, everything has been fixed on the Ondioline (despite it's an instrument that request constant care...), and now she get some friend to talk with !!!
This instrument is astonishing and so expressive. I think in the past years I have a listen at about most video/record available around this instrument, but playing/listening Ondioline for real in a room is another level.

Cheers
Zam

 

[zamproject]

Ho ! thank @abbey road d enfer for the -thumbs up-

I like to publicly thank you for the help around this, PM, mail, talk, all exchange, expertise etc...

Looking forward

Cheers
Zam

 

[trobbins]

Zam, good to hear you are about to restore another instrument, and are still keen for that type of project.

To provide some additional 'insurance' against collatoral damage should parts fail, I can suggest adding a 1n4007 in series with each anode of the 5Z4 - this prevents 5Z4 arcing or stress on the power transformer from that form of 5Z4 failure. Adding a secondary side fuse in the CT link is also worthwhile imho.

Another form of insurance is to add a suitable MOV from each 6F6 anode to B+ (output transformer CT) as a way of suppressing any over-voltage transients that could occur by accident, or gross signal overload, and hence possibly avoiding any insulation tracking or breakdown in the OPT.

You seem to have a tube bias tool for each 6F6 - that is worth checking periodically.

If your hum level is noticeable then there are a few options to further suppress hum.

Ciao, Tim

 

[zamproject]

Tks for the suggestions Tim, I'll think about it

good to hear you are about to restore another instrument,

It's already done ! was faster than the first, due to better electronic condition as some experience gained with the first one

You seem to have a tube bias tool for each 6F6

Nope, but I instal 1Ω on each cathode, last time I check it was OK.
I try 6L6 some time ago, to much power... don't like the feel playing the Ondioline. I'll probably catch some 6V6 duet in my next order.
The new one run on a different tube for the amp, not 6J5 -input- , but direct to the phi stage (12AX7) and an EL84 push pull.

If your hum level is noticeable then there are a few options to further suppress hum

For the 6.3 I do an artificial CT with two 100Ω, with noticeable improvement, feel it was enough so for the moment I don't push further. Maybe one day I'll try with a pot.

As the construction is very old school, with multiple metal frame/chassis used all around for 0V ,and not twisted heater wiring etc... I think it's impossible to have total hum free.

 

[trobbins]

As well as the humdinger pot, another simple step would be to DCV elevate the wiper of that pot. But yes, after that it probably means a close inspection of how parts in a stage are locally taken to a 0V node, and whether those 0V nodes are in a distributed star configuration. I had to do that for my Selmer organ, which similarly had multiple steel sub-chassis and wiring looms and circuit sections.

 

[zamproject]

There is no star or hierarchical 0V distribution in the Ondioline, solid wires are used and soldered all around the chassis.
Components that have a 0V node generally solder at closest location on those wire, without any logical order
So the chassis/frames act like a ground plane and shield ...and safety earth since I add one...
Fully mixed function

 

[trobbins]

Yeh, similar for my Selmer, so I went through and identified if and how I could modify the various sections/chassis to achieve a distributed star configuration back to a single chassis 0V link, along with heater elevations. Some of the original grounding relied on chassis rivets.

 

[zamproject]

This mean a complete rewiring, which I already do once, in the same old fashion way.
I'm not brave enough to do it again right now.

As I say I find S/N ratio not that bad, also most settings involves high and low cut at the filter/resonators bank so hum and hiss are usually reduced there.
In practice for the few sound preset that are quiet and -full band-, that I need to record, I don't care adding a 50/100/150Hz notch filter at mix if needed.

Cheers
Zam