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Tuners - DUAL CT-1440 Upgrade

DUAL CT-1440 Tuner Upgrade

 

I-.INTRODUCTION.

 

The DUAL CT-1440 is a « Papy » borned in 1979 !...it was manufactured when DUAL was still involved in high fidelity. Nowdays, the brand has quite disappeared although it is still alive but its website shows that it does not manufacture "true high fidelity" products anymore, but is more oriented towards car hifi and audio-video devices. This has been the common destiny of all the brands that have not invested enough in quality and brand image...

For our overseas readers, DUAL is an European brand (German), pretty well known until 1985-1990 and targetting the mid range hifi market at that time. Their products did not have a worderful design like their Japanese competitors,  but offered a decent musical quality, although they were not able to compete with the high end brands.

I recently decided to buy a cheap vintage tuner, just to get back the pleasure of listening true FM radios, instead of listening over Internet : the pleasure of a big rotating wheel has nothing in common with a http radio...

After a few time spent on the dedicated site, I found this pleasant looking tuner proposed at $50 !... I like this Vintage look with 3 Vu-meters and a lot of buttons.... As confidence to our readers, I confess that DUAL was alsi the favorite brand of my father a few decades ago, so buying a used DUAL was a sort of « tribute » to my father memory.

CT-1440_front_site.jpg

Given the price I took no risk at all, and I bought it with the idea to offer a lifting to this papy !

 

This tuner offers 4 bands: the classical FM, the MW, LW and much more rare : the SW band.... I will try to catch some African radios in the future...

Much more original, this 100% analog tuner proposes an interesting system to store the stations in 7 available memories... 

 

II-.FIRST LISTENING.

Borned in 1979 : Papy is 36 years old !...

I connect it to my system, tune a FM station, and lesson...

Well... what a disaster ! no life, no energy, no detail... I immadiately thought « Papy is already looking towards the cimetery ! », but you know that Nounours like to revamp and upgrade the devices...

 

 

III-IN THE BOX: THE POWER SUPPLIES.

A review cannot be a true review if the cabinet is not opened in order to check how the device is built and what are the parts used.

Here is a view of what I got for my $50:

CT-1440_internal_site.jpg

 

A few remarks can be made at this point:

  • like it is often the case with the vintage HiFi, there is plenty of available space in the cabinet : this is a very good point for the coming upgrade.
  • the build quality is not as good as the external look may let us believe : the design is modular (good thing) but the quality of the parts is poor : basic caps, crappy cables, crappy diodes, ...
  • these parts are more than 30 years old, so a major replacementoperation is mandatory particularly regarding the caps.

but for $50 I am not disappointed at all : the look is a pleasure and there is plenty of space to work on the upgrade.

But let us go deeper inside in order to deliver a more detailed diagnosis :

First of all, there are 2 power supplies in this tuner represented herebelow, and they are ridiculously small, even taking into account that a tuner does not pump a lot of current :

Dual_CT1440_original_PS.jpg

So we decided to seriously upgrade these power supplies:

  • the capcaitors value will remain the same for each rail, but a 10 times bigger cap from NICHICON KG will be added in parallel in order to increase the available energy,
  • a smal MKP-1843 cap will also be added for filtering

this will give us a capacitance value multiplied by 11 !...This should feed the Dual CT-1440 with enough muscle...

 

Consequently, the new power Supplies design is as follow:

Dual_CT1440_upgraded_PS.jpg

 

For those of our readers who prefer images instead of schematics, here is the view of the original Power Suplly capacitors:

original PS caps 1_small.jpg

 

and here are the photos of the 2 new Power Supply boards that have been installed into the cabinet:

New power supply1_small.jpg

 

and the second Power Supply board:

New power supply2_small.jpg

 

Now we are happy with the Power Supplies !

Humm... are you really sure ? For our regular readers, something is probably missing.... We are talking about the diiodes, and of course we have changed the original rectifier diodes for our high speed, soft recovery diodes.

Here are the photos of these new diodes installed in the CT-1440 motherboard:

diodes2_small.jpg

 

These photo shows the diodes of the second power supply: there is just enough space to host the new diodes and you have to remove the FM board to unsolder the old ones and place the new ones. The red cables are the excellent NEOTECH UP-OCC Teflon insulated cables. At the end of these NEOTECH cables, you can see the new female 1.3mm connectors that we have used.

Exactly the same approach has been done for the first power supply.

 

We have of course replaced all the internal AC cables (which were probably amongst the worst ...), by the same NEOTECH UP-OCC Teflon insulated cable...

 

 

IV-IN THE BOX: THE SIGNAL.

Now we have a decent power supply section, therefore, it is time to look at the signal section. The diagnosis is in line with what we expected:

  • crappy cables
  • crappy electrolytic capacitors, but after more than 30 years, any cap must be replaced...
  • crappy internal connectors and crappy output connector...

The photos herebelow show an internal cable with its connector: the connection is not strong enough, maybe due to the age of the connector. The male pins attached to the motherboard are the standard 1.3mm diameter pins as shown on the rigth picture..

original_cabling.jpg original_cabling_connectors.jpg

 

We have both replaced the cables as well as the male connectors; we have used the excellent (red color on the following pictures) NEOTECH NEI-3004 UP-OCC Teflon insulated symetrical cable, directly soldered to new femelle pins that ensure a strong contact with the male pins attached to the motherboard. This cable is abviously a bit too big because there are 2 cables inside the sleeve, but it was the only one symetrical cable that we found at that time, featuring both UP-OCC copper (including the shield !)  and Teflon insulation.

For the link between the small modular board and the motherboard, we have used a CARDAS Litz enamelled shielded wire, that has 2 disadvantages: it is too expensive and it is very difficult to use (as every enammeld wire...). But at least we know that the quality is there... Only 12 cm are needed to make the link between the two boards.

You can see the NEOTECH NEI-3004 coming from the motherboard to the output connectors on the photo herebelow: look at the big 2 red cables.

new output cables_small.jpg

 

 

The crappy DIN output connector has been replaced by 2 « state of the art » RCA connectors: Tellurium copper and Teflon insulated.

new RCA connectors.jpg

 

Now let us see what we can do for the receiver board. The photo below shows this receiver board, and we have of course changed all the electrolytic caps:

receiver_original_board_small.jpg

 

We have also replaced all the cables coming from the variable tuner cages to this board, by the NEOTECH UP-OCC Teflon insulated cable, using the standard 1.3mm diameter femelle connectors.

There s a second small daughter board for which the DUAL Service Manual explains that the original WIMA 0.1µF capacitors must be replaced by a higher 1µF value in order to ensure proper bass response. Consequently we have followed the Manufacturer recommandation and have installed 2 WIMA MKSA 1µF capacitors. Because the new WIMA are of course bigger than the original ones, we have sticked the 2 WIMAs on the border of the blue connector and use a few cm of NEOTECH UP-OCC cable to link them to the board.

We have also replaced a small 47µF capacitor by a PANASONIC FC. We finally replaced this 47µF Panasonic FC by a bigger NICHICON Muse 330µF (not shown on this photo):

Wima caps replaced_small.jpg

Our CT-1440 Tuner has changed : it looks much more « serious » and we are cloed to the so expected moment, the turn on...

But we have one more thing to do: we have to look on the other side of the motherboard... And we have a few surprimses here: a few crappy cables are used on this face of the printed circuit board.

back_cable1_small.jpg

and another one, maybe an acceptable cable but we also decided to upgrade it because it was not time consuming:

back_cable2_small.jpg

 

Therefore we have changed these cables by our NEOTECH UP-OCC.

 

V-.THE VERDICT: THE LISTENING SESSION.

 

The tuner that we have bought for $50 did not sound pleasant at all: maybe because it has 36 years old and consequently it needed to be restored, maybe because the manufacturer has reduced too much the cost, but it only reached the « 2 stars » category it we had ranked it out of the box ! It missed almost everything: detail, bass, rythm, ....

Now we have seriously wok on it : it was not a difficult work but we expect an improvement. So we connect a FM antenna, turn the power on, and...lesson !

In order to get at least a small burn in period, we let it turned on during one week, because we know that the capacitors require a burn in time..

WAOUH : this tuner now makes music ! It has recovered the missing punch, it makes the difference between the small details, it has get the sense of rythm, it has an alive bass section ! Are you sure that I paid it only €50 ?? The cost of the replacement parts is around €80, but there is no doubt that it is a good approach.

The look of this tuner is definitely vintage with its 3 vu-meters, but its sound is therefore up to the vintage reputation ! This renovation is a total success !

TL_4.jpg

 

This article was written by Nounours - June 2015.


Creation date : 20/06/2015 @ 19:31
Last update : 28/06/2015 @ 14:51
Category : Tuners
Page read 274 times


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