If the non-Motorola transistors are still current parts, then I would expect Digi-key, Mouser etc. in the USA to have these. Or if obsolete, maybe some alternatives, here
https://www.eevblog.com/forum/repair...-function-gen/
Yes, I couldn't work out how to link directly to the photo on that previous thread, so re-posted it here for convenience.
But it would be nice if a zipped-up original-size one could be posted, that the forum didn't heavily compress, so that component reference numbers etc. might be readable.
- As there's surprisingly little on it - other than eevblog I'd linked to, with close-up of the power transistors inc. schematic for those.
The Service Manual for the TG501 can be found as a free download, but despite this being in the same TTI brochure with the TG2001, it does appears to be rather different (much-simpler) internally. Although it does cover mains-transformer connections, which might be similar:
http://www.philipsradios.nl/Schemas/...TI%20TG501.pdf
TTI have some odd-numbering, as the TG2000 is a rather later (still current?) much smaller replacement?, that I do have one of.
- that isn't in the old 'TG2000-series' brochure, that did include the TG2001 & TG501:
https://www.sglabs.it/public/TTi_TG5...000_series.pdf