Lambda Model 28 Regulated tube power supply. Rated Max 300Vdc 100mA and 6.3 Vac 5A.
Just serviced and tested.
Tubes checked.
All wires checked, and re-sleeved or replaced as required.
All resistors checked and replaced as required.
Circuit mods to lower noise from 5mV to uV range.
CLC caps replaced: First cap increased to 10uF oil (was 4uF) and cap after L increased to 75uf (2 x 150uF HF electrolytics) and bypassed with ploypro.
Output cap replaced with SCR 30uF polypro (was 2uf).
Multi component chassis ground decoupling circuit added with ability to connect or dis-connect from HV -DC (original output floated from chassis ground).
6.3Vac output converted to DC with 25A bridge rectifier and 10KuF cap (you add dropping resistor and cap to reduce to 6.3Vdc per your circuit amp need).
This is a great vintage regulated tube power supply from a respected company and highly sought after.
Asking $200 plus ground shipping (unit is heavy).
Just serviced and tested.
Tubes checked.
All wires checked, and re-sleeved or replaced as required.
All resistors checked and replaced as required.
Circuit mods to lower noise from 5mV to uV range.
CLC caps replaced: First cap increased to 10uF oil (was 4uF) and cap after L increased to 75uf (2 x 150uF HF electrolytics) and bypassed with ploypro.
Output cap replaced with SCR 30uF polypro (was 2uf).
Multi component chassis ground decoupling circuit added with ability to connect or dis-connect from HV -DC (original output floated from chassis ground).
6.3Vac output converted to DC with 25A bridge rectifier and 10KuF cap (you add dropping resistor and cap to reduce to 6.3Vdc per your circuit amp need).
This is a great vintage regulated tube power supply from a respected company and highly sought after.
Asking $200 plus ground shipping (unit is heavy).
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It is a real indication of the high quality that Lambda is built to. After 70+ years and a few replacement parts (which you would expect needed replacing after this long of a time) it just as stable and operates like new.
I used this to bypass the solid state HV supply in a Audio Research PH3 and to
say the improvement was nothing less than dramatic would be a understatement.
One thing I did find out, the better the quality of AC cord used with the lambda, the better the sound quality. I used braided 18ga OCC Neotech wire, copper braid shield with a hospital grade AC plug (into a hospital grade wall socket) and it was noticeable. Same goes the connection cable between it and the preamp (braided and shielded Neotech).
For those asking, the chassis ground connection in the picture of the rear binding posts, is the hex nut to the right of the binding strip AC connections.
The binding posts chassis connection (with the jumper to the -DC connection) connects to chassis ground through the multi-component decoupling circuit. This gives you the option of connecting the -DC to chassis ground or floating from it.
I used this to bypass the solid state HV supply in a Audio Research PH3 and to
say the improvement was nothing less than dramatic would be a understatement.
One thing I did find out, the better the quality of AC cord used with the lambda, the better the sound quality. I used braided 18ga OCC Neotech wire, copper braid shield with a hospital grade AC plug (into a hospital grade wall socket) and it was noticeable. Same goes the connection cable between it and the preamp (braided and shielded Neotech).
For those asking, the chassis ground connection in the picture of the rear binding posts, is the hex nut to the right of the binding strip AC connections.
The binding posts chassis connection (with the jumper to the -DC connection) connects to chassis ground through the multi-component decoupling circuit. This gives you the option of connecting the -DC to chassis ground or floating from it.
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