#1
There is an opportunity at the moment for me to buy a 50w Marlin amp for around £30-40, however the amp was built in the 70's but amp is in good condition. Would it be a good idea to purchase this amp or would it be best to leave it as i have no idea what the disadvantages are that come with buying old amps. Many thanks!
#2
Is it valve or solid state?

If it's a valve amp, it will probably need new valves. If it's solid state, it's probably not really worth it.
#3
I think it is solid state. Would it be worth any hassle to get it serviced or is the price of doing so quite steep?
#4
Eh... I'd go ahead and get it. Just see if it works well.
For an amp that cheap (I think that price translates to 70 or 80 bucks american?), with that reasonable wattage, I say go for it.
If it sucks, you could scrap the speakers and make an extra cab for your main amp.
Call me Wes.
Gear:
Fender American Deluxe HSS Strat
Chicago Blues Box Roadhouse
Bad Cat Cougar 5
1957 Gibson GA-5
Ceriatone 18w TMB Combo
Hughes & Kettner Tube Factor
Various Ibanez TS9s
Weber MASS Attenuator