Re: Simon SP5 Valve Reel to Reel Tape Recorder Restoration
Note that when all the valves are removed on an all valve machine, there will be little if any load on the HT supply (s) and the HT voltage supply will go to its maximum value, this sometimes can mean that the HT voltage goes above the working voltage of the connected electrolytics (depending upon the actual working voltage values), so it may not be good to leave the machine running for an extended period with no valves fitted.
On the SP5 it looks like 2 transistors TR12 & TR13 (and possibly others) have their emitters fed (via resistors) from the HT line so this may provide some loading when the 2 valves are removed.
The main HT is shown as +260V, if you have a test meter (to measure DC voltage) I would recommend monitoring (safely) the main HT supply during any initial tests.
When you replace components I would recommend to only replace a small number at a time, then if practical power up and retest to see if any new problems exist.
If you for example were to replace 10 capacitors and 5 resistors all at the same time then find there are new problems, it can then be very difficult (for anybody) to work out whether the new problem (s) has been induced/created by the repair work.
David
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