nice to see you like this amp. I have serviced around 50 4650 by now. There are some more things people should worry about. The power caps are often degraded to less than 50% of their original capacitance. The relay is very unreliable... the clamp which holds the 4 contacts in place tends to fracture pushing the contacts against each other, resulting in fireworks. The original bias trimmers are unreliable. So are the original capacitors after more than 40 years of age. The amp can play fine on regular transistors by the way. I normally use them for test purposes.
Lovely Sony. I've got an STR-6060FW, their statement receiver from 1968. It's a great piece that I enjoy very much. You've got a great channel here, as a vintage audio fan but engineering illiterate, it's really interesting to hear your explanations of the circuit design from a tech perspective.
Hi Toby, thanks for that great feedback, very much appreciated and glad you are enjoying the channel! Much more over at my website - liquidaudio.com.au.
Liquid Audio cool, I'll check it out. Do you know of any resources for starting to learn amplifier tech/basics, or is that considered trade secrets? : p might be a good video idea. It's surprisingly hard to find a good guide, I get the feeling a lot of people learn as they go in this hobby.
Hi Toby, another great question. This is definitely not considered trade secrets, but it is surprisingly hard to find any useful resources on this type of thing. That is part of the reason for starting my own website and youtube channel, with articles about the work I do repairing hifi electronics.There are some great learning electronics websites that will come up with some googling. Taking an engineering or electronics course might be helpful, and there are some great youtube channels like EEVblog, The Signal Path, and Mr Carlson's Lab. You'll find some good electronics basics and troubleshooting videos on all of those channels, all three guys are very knowledgeable and present content in a very user-friendly way. Check them out if you haven't already!
Rui Barbosa Hi, yes there are potentially other things that could be done, but I operate conservatively and like to keep things original where possible, whilst enhancing reliability. The power supply in this old girl is perfect, spot on voltages everywhere. I neglected to mention that I also mounted the VFETs on silicone thermal pads!
Hi Mike - great vid - (you are an Ozzie? I am in NZ). I bought a 4650 and a 5550; the 5550 has the proper rank VFETs installed however the 4650 VFET ranks are all over the show, I dont think any of the VFETs are in the required Sony rank range....it still works however....I am about to overhaul it - starting by measuring the existing VFET bias - I coudl get lucky and the mismatched outputs are drawing the correct current. The service manual is confusing as hell by calling bias setup "DC bias" - which involves putting a probe on one speaker terminal? But your vid confirms that we are indeed measuring output bias using this method (as opposed to DC speaker offset!) thanks!
Hi I have just found a 4650 It plays fine through the headphone, haven’t tested with speakers. I read everywhere that these units “blow up”, if get sound out of it, does it mean it isn’t blown? Basically how do I know if the vfet are blown or not? Thanks
Hi, great purchase, these are lovely amps! All the VFET Sony amps are prone to failure until they've been slightly modified and have the Sony-recommended service improvements implemented. As with anything technical, this work should generally be undertaken by an experienced technician, especially here, given the irreplaceable nature of the VFETs. Likewise, VFET testing is best left to someone familiar with their handling and testing. VFETs, whilst actually robust devices, are fragile because they can be damaged by static electricity.
@@soulpixel Agreed, if there is no distortion, things are at least working reasonably well. You then want to have the service adjustments and reliability enhancements implemented so that she continues to run well.
Hi, Great video! Thank you. I am in Qld, Australia. I have this amp. I changed the dangerous diodes as per a whole range of pretty simple and consistently similar instructions via internet. And it has, and continues, to work beautifully for about 7 years now. No issues!! What I'd like to ask you relates to a similar amp I bought here in Australia - the Sony TA-5650 v-fet amp. I bought it from a nice guy who refurbished it with great care, many difficulties and much frustration. It worked great for the first few months, but then started to get super hot along with a burning smell. It would then shut itself down, thankfully. Can you give me any advice. I could even ship it to you for a look. Kindest regards John
Hi John, it sounds very much like this amplifier needs some TLC. I strongly suggest you don't use it until it's been properly fixed. Diagnosing anything like this remotely is problematic, she really needs to come in for testing and diagnosis. I'd be very happy to assist, the problem is the distance, secure, double-boxed insured shipping with a quality provider like Pack & Send isn't cheap. The VFETs are almost unobtainable now, so you don't want to do anything that might jeopardize a good set. Visit my website for my mobile number if you'd like to call to have a chat about this one. I'm open from 10am to 5pm Perth time, Tuesday to Saturday.
Hi Farzad, I cannot give prices on items like this, it depends on a range of factors like whether it contains its original VFETs, service history, current condition and market factors, including where you are. A perfect example though would sell for many hundreds of dollars in most cases.
Farzad Monadizadeh As mentioned, there are too many variables for me to provide anything other than a rough guide, which I’ve done. Your best bet is to let the market decide with something like eBay!
I have a TA5650 Vfet that belonged to my Dad, I have hooked it up to a cd player and 2 speakers and it seems to work. Is there more to it than that? Would it still work if it was blown etc?
tom thorne Hi Tom, there is more to it than that but if it was blown it wouldn’t work as it is, so that’s positive. It may have been repaired previously. You want to have some reliability enhancements done, because it will blow eventually and there are no viable sources of replacement output devices when it does.
