Unold Backmeister difficult to switch on

Probably one or more electrolytic capacitors. Do you have an ESR meter?

Unfortunately I do not have an ESR meter available. I know a hw repair shop though. One limitation I could foresee for who may help to assess is control board is not easily accessible. Could be seen here:

Few more tidbits. Yesterday I kept the machine connected to the mains for two hours before actually using it. One hour and it finally went on. One more I loaded it and went through the program without a hitch. This unlike the previous occasion when I operated it only minutes after switching on and had to be re-started twice.

Also I mentioned yesterday text on the small display was quite faint right after switching on. It was sharper and easily read by the end of the program.

What is the useful shelf life of electrolytic capacitors? I was wondering if the - potentially already old - replacement board offered by the producer would be a suitable replacement. Or fixing the existing one would be the better option.

Isn’t about total cost but about keeping something useful working for much longer. I could buy a new one for marginally more than fixing it.

Sorry this isn't more helpful but - it varies from manufacturer to manufacturer, from type to type and from application to application. Sometimes their working life is specified at certain temperatures, but the relevant literature is not always available and shelf life is hardly ever mentioned..

A capacitor that might last indefinitely as a decoupler in a pre-amp could fail rapidly if it were in a power supply with high pulse currents. Even if it started to fail, as a pre-amp decoupler it could degrade quite badly before any drop in performance would be noticed, whereas, in other parts of the circuit, any leakage would result in "noisy pots" or some other very obvious symptoms.

Furthermore, a manufacturer with a good reputation might have an occasional dud batch or may be take over by bean-counters and start producing 'value-engineered' rubbish without any visual change in the product. It would only be much later, when things began to go wrong, that their reputation would be lost (and by then the bean-counters would all be retired with fat pensions).

Well written and thanks.

Any hint from my previous posts about why I am experiencing described faults? Delay at powering on expanded from a minute to an hour after only two use cycles.

I am not familiar with the product but that time-scale suggests something like a memory battery or super-capacitor needing to charge up. Does it have a memory battery?

If it hasn't got a battery, then a failed electrolytic capacitor would definitely be my next suggestion.

If you replace the capacitors, use 105C ones.

It does have a memory battery to store custom program settings. To my surprise it didn’t fail so my settings were retained. What changed instead is the power up - not instantaneous anymore - the text on the small segmented display - faint after switching on, less so later - and occasional resets along the program - happened twice the same day but not the next day when power up was much earlier than program start.

I can't really make any helpful suggestions as I am not familiar with the equipment. If you can measure some of the voltages (start with the battery) you might find one that is low and only rises grasually.