Leak 3400 refurbishment January, 2023
This Leak 3400 is for sale in the Netherlands, fixed price 250 Euros, cash and Local Pickup as I do NOT ship,
I only answer if you provide your phone number also, see the moving mail address on my main page.
Gemakshalve is deze pagina verder in het Engels geschreven.
This page is written using English language only.
This nice wide form factor "vintage" Leak 3400 was refurbished and modified, just a leisure project....
It has a nice thick aluminium front plate. Its knobs are machined solid aluminium, no plastic, here....
The enclosure is covered by some "plastic veneer" stuff. Therefore, after the restoration, I put a layer of polymer "floor protection fluid" on it. I am rather enthusiastic about this product, it just make things looks newish, without affecting the color.
The innards of the not-yet-refurbished receiver.
No mechanical wearout, no burn marks, no weird construction, simply a well designed receiver.
The Leak 3400 power supply
The power supply appeared to incorporate a voltage doubler, apparently the manufacturer decided to take the capacitor off-board and glued it to the bottom chassis.
Probably it was failure-prone, as there is AC current flowing "through it", and it must be kept cool. Now, the series transistor has to get rid of more than 30 Volts. If they had not used this way of rectifying, they could not use the simple way of smoothing power for the preamps.
While the middle picture indicates a capacitor location, two leads go down from it, on the bottom of the receiver they go to a big 80V premium quality capacitor, apparently needed.
The circuit was modified to get rid of the voltage doubler.
Wanting to make a low drop regulator, I wanted to use a PNP series pass transistor.
The easiest way to draw was taking an easy schematic from the internet and adapt it to the desired voltage (27.5 Volts).
New premium type 15000µF power smoothing capacitors were used, so a more capable bridge rectifier was needed than the 3 Amp diode set used, originally.
The power amplifiers board
A little bit dusty, but still in good shape.
The old transistors are still good but HFE was on the low side.
Notice the type identification plate: the receiver is made for the Rank conglomerate. Removing it, one will see the voltage selector plug. I kept it at the 220 Volts setting, to gain a few output watts (mains is around 230 Volts, in the Netherlands).
The Quasi-Complementary power amplifiers used a double diode pickup mounted on the heatsink, it was routed to a VBE multiplier transistor on the circuit card.
As all over the internet it is said the incorporation of a "baxandall diode" has benefits only, I implemented it.
The result was a situation the old bias circuit being obsolete, so I mounted a VBE multiplier transistor BD329 directly on the heatsink, using a heat-conductive ceramic insulator.
Pins 4 and 6 did get a 3k83 resistor in between, it attaches to the base and collector of the BD329.
The diode hides behind the PNP driver next to the emitter resistor of it, this resistor was 22 Ohms originally, but it is 330 Ohms, now.
New power transistors:
New parts were used as thought appropriate.
RIAA input circuit card.
This card has a metal shield. (removed for picture)
It uses a chip designed for the very purpose of being used in this kind of circuits, there is not much to be gained here and just the electrolytic capacitors were replaced using ones assumed a good choice.
Of course, also here, superior film capacitors are used instead of capacitors, if viable for size versus amount of room.
Pre-amplifier board.
I forgot to take pictures of this part of the recap, also here this was capacitor replacements only.
As all potentiometers and switches still operate very well, these were untouched (not cleaned).
The Tuner boards.
The tuner related circuit cards did get a recap for the aluminium electrolytics only, using parts I considered appropriate.
The receiver backlighting.
The old lighting was intact, but some lamps were blackened already. Again, I went the LED-string way.
There are the two meter mounting brackets and the scale backlighting, carrying the led-string pieces.
The LED string piece stick out a bit at the meter brackets, as they have to be cut against the marks provided on the LED-string.
The color is warm-white "2700k". A LM317 adjustable voltage regulator is mounted on the bottom of the power supply card, to provide LED power.
Testing brightness versus voltage and current, and the LM317 on the bottom of the power supply board.
The Amplifier protection circuit.
This receiver did not employ any loudspeaker protection, so I decided to add it.
Three possible solutions were were evaluated:
- The solutions described on the well-known Elliott Sound Products pages.
- The one used in many Pioneer amplifiers and receivers.
- The one I used before, alike the Tandberg TR2080 one. I decided to use this one.
The schematic employs DC detection as well as AC-loss detection to immediately switch off the realy when the receiver looses power or is switched off. A zener diode in the relay snubber circuit dissipates energy to enhance relay switchoff speed.
- A LRE 10 AMP avionics relay is used, it is mounted in between the power transformer and the power smoothing capacitors.
Just imagine, the new price of such relay is now higher than my price for this receiver.....
The stripboard, containing the circuit. I managed to keep it very small. Even transistor selection was done with the pinout versus mounting location in mind, to get the smallest footprint considered the parts used.
The back of the receiver.
Whereas no decent DIN loudspeaker connectors are to be found anymore, a set of others was mounted.
The bottom.
The Front. The receiver does not look that big on the picture, but it is quite wide.....
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