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PostPosted: 29 Aug 2017, 04:46 
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We cannot all be perfect. Slowly loosing my Russian as I practise so very seldom ...

A photo of the transformers I have. Honestly the Lundahl mains transformer doesn't look nice at all and have to be hidden inside the chassis. The OP transformers don't look good either. They had originally just a piece of steel, enough to be screwed in place welded on the underside. Then I glued long screws in the mounting holes and now I had to cut and bend pieces of aluzink to fix the transformers.
I had nicer looking transformers but I think I sold them.

Attachment:
IMG_3339.JPG


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PostPosted: 29 Aug 2017, 13:17 
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Soundbrigade wrote:
We cannot all be perfect.

I do not ask that :) Just put my 5 cents on this topic. Very interesting, by the way :up:

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PostPosted: 29 Aug 2017, 14:33 
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I am really a tubfan, but the arrival of these small (in size) and big (in sound) and low (in prize) has really gotten me going and I want to test all variations.
But I have come to a halt. The latest ones, the TPA3118 don't work as I expect them to do and I have an idea what's wrong.
Here's what the datasheet says about the inputs (of the actual chip):

Attachment:
Tda3118_IP.gif


I have no clue how the inputs are arranged on the boards. Are there caps connected or not?
Well, I experience a loud distorted sound even when the volume control is turned all the way down. Even swapped it with another one (50K log). Tried my switched 30V/5A PSU AND a 12V 18Ah battery - no difference.

AND, I haven't taken any photos yet, but I have a photo from our tour to Russia this Summer.

Attachment:
IMG_2513.JPG


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PostPosted: 30 Aug 2017, 11:47 
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Back to some sober discussions ... :yumcoffee:

I accidently soldered the board today. For once, everything went smooth apart from a miss in the marking on the PCB. One of the 220K resistors was marked 270K, but a thorough check showed that the marked resistors must be 220K. And to make a link to a question in another thread. All resistors are 1W as I wanted something substantial to work with and to avoid all problems from physical small devices and strong electric fields. Caps are also (in most cases) to specs. Plastic caps are ... plastic caps.

Attachment:
IMG_3350.jpg


And the BIG issue; how to mount the sockets.
Below the chassis, directly on the PCB. Advantages are that the PCB can easily be removed for service or upgrading. Disadvantage is the the tubes aren't fully pushed into the sockets as the chassis is some 2mm thick.

Attachment:
IMG_3348.jpg


On top of the chassis - Looks neater but almost impossible to access and repair.
Both ways means that the assembly is, by the sockets, fixed to the chassis.

Attachment:
IMG_3349.jpg


Note, that the sockets will be flush with the chassis top.


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PostPosted: 31 Aug 2017, 01:41 
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Talking of sockets, got a reminder from Finnish Ural-Tone yesterday: You've got four octal sockets for PCB mount in the basket. Do you want to check out? :(

And idiot me, why didn't order the missing 22uF/400V caps as well. :eek:
Think I managed to add them after all, let's see how that worked out.

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PostPosted: 24 Sep 2017, 12:22 
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Loved that comment! :down:

a) Had almost forgotten about this thread
b) Have to get away from a crazy discussion in a Swedish HBTQ/BDSM-forum (DON'T ASK! :blush: ) about polygami (*)

So this project has marched forward much faster that I indicated. The board is ready, the top plate is almost finished (made a mistake drilling the holes for the grommets today, but that is nothing to care about). Some of the holes for fixing the sockets has to be filed a little to get the screws in place.
Some soldering is left - wires to the trannies and whatever more is needed. And a wooden box to hold the amplifier. Power transformer to go into the box.

The sun has disappeared in heavy clouds so I am using un-natural light.

Attachment:
IMG_3449.jpg


Transformers are Chinese 10K Raa - Eagle-something.
Attachment:
IMG_3450.jpg


Attachment:
IMG_3451.jpg


Came to think of it - I have a typical transformer for use in classrooms:

Attachment:
IMG_3441.jpg





(*) That crazy discussion made me :mad: . When I express an opinion, people immediately come up with the super-phrase: "... then you also say that you mean ....."


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PostPosted: 24 Sep 2017, 12:24 
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Ah, you noticed that. The transformers may be very close to the tubes, but I had actually planned to use Hammond 125E and they would be placed 1/2" further back.

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PostPosted: 24 Sep 2017, 13:29 
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Soundbrigade wrote:
b) Have to get away from a crazy discussion in a Swedish HBTQ/BDSM-forum (DON'T ASK! :blush: )


Quackti will pwn them :smoking:

Quote:
Attachment:
IMG_3441.jpg


I'm imaginine an AC line cord with banana plugs :hot:

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PostPosted: 24 Sep 2017, 15:25 
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Quote:
I'm imaginine an AC line cord with banana plugs :hot:

Not a big problem, it was used in an isolated environment - junior high .... :thumbsup:

I have an idea of stuffing the tranny in a chassis so I can use it for other purposes/amps. It was given to me and now that I came to think of it, I realised how handy it would be. But NO, I don't see it a safe thing. And I have a another transformer for this guy. The not so nice looking Lundahl tranny that was also something I got.

Image



OT: About the odd forum ... have you seen my Quckti? ... I joined it hoping to sell some corsets (don't ask!) through that channel.

Here's Quackti:
Image

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PostPosted: 24 Sep 2017, 16:58 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
HI, I have seen prettier trannies for sure. On the sockets...probably too late now but they make ones with long legs for PCB mount and they would seem to be what you need. I believe you can also attach the metal collars to them and that would allow mounting from the bottom of the chassis. Biggest issue would you would have to consider the exposed legs for hum and noise pick up as well as possible oscillations.

Good listening
Bruce

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