Vintagehifi.dk

Hello everybody,

Sorry for the English, my Danish is very bad. I hope someone can help me further on my path to restoring this machine. I got the Arena T9000 (by Hede Nielsen) from my parents, it was stored for a long time. Unfortunately there is a lot wrong with the machine. Both outputs are blown and the tuner is dead. Of course the gears from the tuner are disintegrated but I was able to 3d print two new ones.

To be able to fully restore this machine I am in dire need of a service manual. I did find schematics but that is only part of the story. I tried to contact a technical museum in Horsens but never got any reply.

Perhaps someone knows a place I might contact for the manuals? Or perhaps someone has them and would be willing to make a copy? I can pay for them as this machine was very dear to my parents.

Many thanks!

Bert from The Netherlands

Try PM'ing member "tube mania", he has one he restored; or maybe "MaxJ" can help with a manual?

Brgds Klaus

I have a manual on English on PDF. Send me a PM.

Many thanks for your responses! I have contacted Max and hope we can come to an arrangement.
I believe these T9000 machines are very rare and I have the experience & knowhow to restore it.
But without a service manual I would be flying blind and these ancient machines are very finicky.

I do like that they have encapsulated most functions into 'modules'.
I think this must be an Arena specific thing, can't imagine they would design such a feature for one machine only.
But right now most of these are just black boxes unfortunately.

Many thanks,

Bert

I have sent you a message, if you have not received it, write right here.

Hi all,

with the service manual I was able to rebuild the end stage of the amplifier. Someone had already been working in there so without the service manual I was flying blind as to what was the original implementation. As the manual also has the instructions for the calibration all is now working within specs.

Next up this weekend is the tuner (FM is dead). Then I need to look at the modules for the AUX ports as these appear to be pre-stage amplifiers. Problem with this is that if you connect a CD-player (a modern device) it will be completely overdriven. Basically those AUX ports are more suited to a turntable, that is what the module tells me. So I need to device a way to either bypass one module or design a different layout.

Wish me luck :-).

Many thanks again,

Bert

Try a 10-20 dB attenuator in Series With the cd-input

his067 skrev:Try a 10-20 dB attenuator in Series With the cd-input

Yeah tried that already but the amplification on the input it still way too high. Both AUX ports have a "Modul" attached to them and the topology of that module is akin to a phono equalizer / pre-amp. So the signal that is entering this stage will get amplified by a lot (I believe it is a BC550C equivalent transistor in there). I need to think about an elegant solution for this as I don't want to yank the module out for a straight bypass.

Bert

Hi Bert,

You mention that your AUX ports are suited for turntables, then we know what the problem is.

The typical turntable (phono) input is expecting about 2-4 mV @ 1 kHz and has frequency response correction (RIAA) of about 40 dB across the 20 to 20.000 Hz frequency range. Even with a large attenuation from the CD players typical 1V output, it will never sound good due to the RIAA frequency response. So you need to find a suitable line input module that fits the typical AUX input level of about 100 to 200 mV, which was the norm in the 1970’ties gear. With such an input you typically dont need an attenuator between the CD and the amp.

I hope this makes sense

Best regards Kenneth

Hi Kenneth,

Yes, the two AUX ports are essentially amplified with a single stage amplification module. A modern cdplayer will cause havoc on those ports. As far as I can tell, based on the age of the machine, these were meant for a turntable or some other equipment that needed amplification.

I have designed a 'new' module that is basically a line input dampener and filter. The modules use a special foot to insert them into the socket. I think these are based on the old standard for tubes. So i'll need to source something that is the same size and has the same pins. Or butcher an old tube somehow. PCB's should arrive next week so i'll take it from there.

Thanks for the input!

Bert

Ps: if anyone needs a 3d print of the gears in this machine just let me know. The old ones are usually desintegrated.

Interestingly, I found a solution. In my box of 'forgotten electrical appliances' I found a QED CD-control unit. It is a tiny passive pre-amplifier with a volume control. Basically it is specifically designed for cd-players and an input-output limiter with an attenuator. And it works ;-).

I can limit the input and thus the output to the amplifier modules; it is almost at zero volume output. Now I can jack the volume of the T9000 to a normal level without heavy levels of distortion.

If you find one of these (I bought this for €1 at a flea market) I recommend it for this kind of purpose. I actually can't see any other purpose for this little box than what I am doing right now ;-).

Will still build the new Modul of course (still need to source the vacuum tube legs).

Bert

You may want to defeat the (normally undefeatable) loudness curve that is built into the circuit around the volume pot. It can be overwhelming. And remember: High efficiency speakers (such as horn loaded speakers) do not go well with the Arena: I used to have a set of Lowther PM2As in a Super Ace horn hooked up to the Arena. the background hiss was insufferable....

his067 skrev:You may want to defeat the (normally undefeatable) loudness curve that is built into the circuit around the volume pot. It can be overwhelming. And remember: High efficiency speakers (such as horn loaded speakers) do not go well with the Arena: I used to have a set of Lowther PM2As in a Super Ace horn hooked up to the Arena. the background hiss was insufferable....

Ah so there is a loudness circuit after all, I had a suspicion about this but did not pursue it. Many European manufacturers did this somehow, never understood why as it colours the sound where you obviously don't want it. Let me check what I can do about this.

As for the speakers, I can testify about this indeed. But right now it is only connected to my trusty bench speakers. They are far removed from anything hi-fi and only 82db efficient ;-).

BB

I've got the FM tuner up and running again. Sadly it is still not functioning very well.
Sensitivity is very low and just a few stations received. Also the tuning strength meter always starts at level 3.
So, first success but a lot more work still to do ;-)

BB

It is more than forty years since I passed the T9000 on to a friend, but if memory serves the volume pot has four connector pins. My recollection is that one of these needed to be lifted out of the circuit. But that is as far as I remember ("I was young and happy as the grass was green...." see if you can place that quote. It is from one of my favourite poems)