Techy board - re-capping

[Wakefield Turntables]

Pcb can be bought for fifty quid on scumbay

[Gmanuk101]

Pcb can be bought for fifty quid on scumbay

a brand new one?

[Wakefield Turntables]

No

[UV101]

There's nothing wrong with a functional 2nd hand board.

The thing with electrolytic caps is over time they dry out. This will cause the specs to go out and the first thing to change will be the esr of the cap. The effect of this will be that the rails they sit across will start to become noisy which in turn will effect the performance of the circuit. There have also been advances in technology and materials in the last 20 years. Some of the new solid polymer have almost unbelievable esr specifications. Most of the time the caps will have been chosen based on price. I a circuit functions within specifications with a 1p part why use a 10p part even if this does improve the overall performance.

Replacing the caps with newer technology should make the circuits perform "better" which in turn should lead to a more stable and accurate control of the platter. Clearly along the way technics replaced the conservative power supply smoother (c1) with and even more conservative value part. The deck will still perform within the specs but the change in value from 1000uF to 470uF will have been purely based on cost. There is no other viable reason.

In any external psu, the value for the equivalent part is likely to be at least 10x that value because its not an expensive part on its own and a larger value will allow the psu to better (faster with more reserve stamina) deal with any peak current requirements.

One downside to making the value large is that the inrush of current required to charge the cap at switch on could mean that a bigger more powerful transformer is required along with bigger rectifier diodes. It's often that case that as you upgrade a component, you will also need to upgrade any supporting components.

I will shortly post the full diagram with my own recommendations for cap changes. It's not going to be expensive to implement as as a few have pointed out here, they've already experienced benefits of psu cap upgrades.

[Qwin]

[Wakefield Turntables]

It's quite exciting I'm looking forward to see what gets published here

[Frankyc2003]

This place gets better everyday!

[UV101]

little bit of the work in progress just to get you on the hook

I've stitched together the various parts of the diagram. I don't think a complete diagram exists anywhere like this.
I've also started to show the various power supply rails in different colours and mark all of the electrolytic caps on the diagram
Next I'll mark the same caps on a photo of the PCB and finally put a list of recommended replacements together.

[Thirsty Dog]

There is some pretty dam fine information coming up here.
Although I'm a complete modding novice, I would certainly give it a shot on my own, after a bit of practice with a soldering iron on a test PCB.

Looking forward to what follows.

Great work UV101

[vandergraafuk]

+1 for the great work