I restore vintage tube radios and amps electronically and cosmetically. My grandfather was a tv and radio repairman and I learned that skill from him. I have many tools and diagnostic equipment I use to test a radio that someone trusts me to repair, oscilloscopes, mutual conductance tube testers, signal generator and a variac just to name a few. 9 times out of 10 the problem is because the original paper capacitors are bad so I begin by replacing all the capacitors and electrolytic capacitors with their modern equivalents, replacing them should always be done regardless of what is wrong with the radio because a bad one will ruin an expensive transformer and the vaccuum tubes making what would have been a relatively inexpensive repair very costly. They are cheap and easy to replace, an analogy would be like driving with dry rotted tires. I then test all the resistors and replace any that are not within the original factory specs that's listed on the schematic, usually +/- 10%. I then test all the vacuum tubes and replace any that are weak (I don't replace them because I'm guessing they are weak). I check all the wiring and then realign the tuning capacitor. Plug it into the variac and slowely bring the voltage up and I would estimate that 98% of the time the radio works like it did when it left the factory..there are more steps to restoration but this is the condensed version. Sometimes the issue requires more advanced use of my diagnostic equipment and the reliance on my years of experience. When a customer explains to me the symtoms of what's wrong with their radio or amplifier I have enough experience and skill to know where to start looking. I don't randomly replace parts in the hopes that it solves the issue. I would never randomly throw parts in a radio and then tell my customer the radio was fixed when it wasn't, I would be embarrassed to do that. I would also never tell them that I don't know what the issue is so I'm just going to keep replacing parts until it works. That's a sign of inexperience and ineptness and it's also terrible business. I'm a professional and if I cannot fix the radio I wouldn't charge a dime or expect that customer to come back just because I had hours of diagnostic time into the radio. The dealership did not offer to refund my money or give me service credit for their misdiagnosis until I asked, they threw up a "test ballon" to see if I would roll over, that's terrible customer service. I only took my vehicle there in hopes that it was a driveline issue and covered under my warranty. The dealership is more concerned about the bottom line and who is going to get paid and have the production line mentality of getting cars in and out quickly rather than customer service. They are inexperienced and inept and it's my money and it will be given to a professional and experienced mechanic. So tell me again why I should throw my money at a dealership whose inexperience and ineptness failed to diagnose my car in the four days they had it and their next step was going to be to randomly replace parts until the issue was corrected...on my dime.