[gjo1314]

Frank

I am considering upgrading an ST 70 clone that I have( it was bought a few years ago) but never worked well from Day 1 because of very poor initial assembly by someone not experienced in such equipment. I would like to use the chassis, the transformers, input and output jacks, and rectifier tube as well as the EL 34s and anything else that I can salvage. It works on 220V AC mains power.

If I were to order the U70 kit from you-I now have access to a very experienced technician who has extensive experience with valve amps- what else might I need to get this up and running?Also does running the 220V version of the ST70 require any changes to be made into your kit?

Please advise.

TIA

George
Bangalore, India

[gjo1314]

I didnt add that the speakers that I am using are 87dB, currently being driven by a KT 88, 55 wpc integrated amp. I plan to use these speakers with the ST-70, they use Scanspeak drivers.

[avahifi]

The Ultimate 70 rebuild kit replaces the audio circuits, the quad filter capacitor, and the bias supply circuits.  It requires properly working and wired transformers and the power and tube socket wiring.

If your amp is poorly wired, normally simply going over every single solder connection to the tube sockets, etc. will take care of that issue.

Does the amplifier properly bias set now at 1.56 V DC per the Dyna instructions?  Low bias usually means weak output or rectifier tubes.  High bias often is a defective output tube.  Make sure the 15.6 ohm precision resistors from the tube sockets to ground are still working at the correct values, and that the ground connections there (the tube socket hardware) is really tight.

If your power transformer is a 220V version now, then the Ultimate 70 kit will work just fine with no modifications on 220V AC.

Note that all the "hardware" such as transformers, chokes, tube sockets, etc. is available from www.dynakitparts.com and other sources.

We suspect you will find that the Ultimate 70 rebuild project will exceed your expectations.

Frank Van Alstine

[gjo1314]

Thanks Frank..

I have spent  a lot of time trying to fix it, but whatever the reason, it has never stablised, so I will do as you suggest, while also checking out the transfomers-these are good output trannies from Magnequest, and should, in my view be put to use, and not lie around gathering dust as they have been doing! Mike at MQ has given be the steps to follow to check them out..

Currently how long would it take you to ship out an Ultimate 70 kit to a US address( my son), after order is placed and payment made?

George

[avahifi]

We can ship an Ultimate 70 kit within two days of receipt of order.

Agreed, the Magnequest output transformers are the best we have seen for the Dyna St-70 chassis.

Thanks for your interest.

Frank Van Alstine

[rlee8394]

Agreed, the Magnequest output transformers are the best we have seen for the Dyna St-70 chassis.

Too bad these are out of production and very hard to come by.

Ron

[avahifi]

Actually the Ultimate 70 kit gives outstanding results with any of the Dyna output transformers available.  The Magnequest units measure the best of any we have tried (have not had a look at the Dynakitparts units yet), but all work very well musically, nothing major to worry about.

Regards,

Frank