The LEAK Delta 70 amplifier, a guided journey

[leoredi]

Dear all,

I have read this forum for a long time and finally decided to get my hands dirty. I waited until I could find an amplifier I liked and bought one, I decided to buy the LEAK Delta 70 amplifier, one that did not have too many problems.

My unit sounds good only problem I have found is a strong channel imbalance, in order to have balance between the two channels the knob has to be rotated 45 degrees, I therefore think there is a problem.

I will start de-oxing the knobs but I have few question to you before I proceed.

1- This is the most important one: when do you actually have to replace the capacitors? I photographed some capacitors that I think need replacement [1] [2] and some other that I they do not [3] [4], do you confirm? Is there an actual test one can do in order to make a judgment or do you just use eye inspection? I am especially in double for [4].

2- I think that the main plug is an aftermarket fix and I also this is dangerous because the amp is not earthed, do you advice in just replacing the plug by cutting the wire? Or should I just leave it and earth the amp from the casing?

3- There are some part which have particularly bad oxidation (also here), in these cases do you remake the connections or just give it a clean?

Here is the link to the full album of pictures.

Thanks a lot guys, I will of course keep you posted whit any news...

Best regards,

Leo

 

[rlisin]

Welcome to AK. You got a fine amp, I have a Delta 70 and it's one of my favorites.

Cleaning pots and switches is definitely a good idea. This is one of two most likely causes of channel imbalance in this amp. Pay special attention to switches, they cause such problems more often than pots. That includes switches on the back (but those affect individual inputs, so if you have imbalance across the board, the problem is elsewhere).

I would leave the caps alone for now. They are not obviously bad, and if my Delta is any indication they could all be OK. There are other things to check first.

My Delta has a (different) plug without the earth pin. Works without problems. I wouldn't worry about that.

The discoloration in your pics could be rosin. You could check the connections and reflow them, but they're probably fine as it is.


Now to the second common cause of problems in Deltas. You noticed that the amp is modular, preamp and power amp driver boards are not soldered/wired, but plug-in, connected in slots (like in desktop computers). A very common problem in Leak amps are these slots. Take out all boards (remember which one goes where) and clean contacts on the boards and in the slots. Especially the slots need to be cleaned thoroughly and then dried. Then put the boards back and try the amp again. If the imbalance is still there, you can try switching boards between channels. There are 2 pairs: 2 larger boards are preamp channel L and R boards, 2 smaller boards are power amp channel L and R, so it is easy to switch circuits between channels to isolate the problematic board. The order from left to right (looking at the front of the amp) is: L pre, R pre, R pwr, L pwr.
If you switch boards between channels and the imbalance moves, then the problem is on one of the boards you just moved. If you switched botch pairs of boards and the imbalance stays the same (the same channel is weaker) the problem is somewhere else, not on these 4 boards.

Hope this gets you started.

Have a look here, a lot of helpful info + diagrams:

http://www.angelfire.com/sd/paulkemble/sound7h.html

Also, hifiengine.com has a service manual for Leak Delta 70. It's free, but you'll have to register.

 

[liemjerry]

Welcome to AK. You got a fine amp, I have a Delta 70 and it's one of my favorites.

Cleaning pots and switches is definitely a good idea. This is one of two most likely causes of channel imbalance in this amp. Pay special attention to switches, they cause such problems more often than pots. That includes switches on the back (but those affect individual inputs, so if you have imbalance across the board, the problem is elsewhere).

I would leave the caps alone for now. They are not obviously bad, and if my Delta is any indication they could all be OK. There are other things to check first.

My Delta has a (different) plug without the earth pin. Works without problems. I wouldn't worry about that.

The discoloration in your pics could be rosin. You could check the connections and reflow them, but they're probably fine as it is.


Now to the second common cause of problems in Deltas. You noticed that the amp is modular, preamp and power amp driver boards are not soldered/wired, but plug-in, connected in slots (like in desktop computers). A very common problem in Leak amps are these slots. Take out all boards (remember which one goes where) and clean contacts on the boards and in the slots. Especially the slots need to be cleaned thoroughly and then dried. Then put the boards back and try the amp again. If the imbalance is still there, you can try switching boards between channels. There are 2 pairs: 2 larger boards are preamp channel L and R boards, 2 smaller boards are power amp channel L and R, so it is easy to switch circuits between channels to isolate the problematic board. The order from left to right (looking at the front of the amp) is: L pre, R pre, R pwr, L pwr.
If you switch boards between channels and the imbalance moves, then the problem is on one of the boards you just moved. If you switched botch pairs of boards and the imbalance stays the same (the same channel is weaker) the problem is somewhere else, not on these 4 boards.

Hope this gets you started.

Have a look here, a lot of helpful info + diagrams:

http://www.angelfire.com/sd/paulkemble/sound7h.html

Also, hifiengine.com has a service manual for Leak Delta 70. It's free, but you'll have to register.

Hello sorry jump into this conversation, need information about DISC mean, is those 2 inputs for Phono Turntable? also need info for speaker connector that also weird for me, do you use special connectors?

thank you