337alant
Negatively Biased
I have started on a complete service & calibration of my Technics RS1500 US Reel 2 Reel
My model has a Record Playback on the 2 track heads and playback only on the 4 track heads so very versatile
These are a beautiful R2R with a unique tape handling transport
http://www.thevintageknob.org/technics-RS-1500U.html
The speed stability and W&F are excellent due to the quarts Phase locked DD capstan drive motor with twin Capstan Roller tape drive.
Being manufactured from 1976 to 1981 they really were quite advance for their time but show their age with the simple belt driven counter
IMG_1948 by Alan Towell, on Flickr
So as some of these decks are over 40 years old they have started to suffer from Capacitor failure, particularly the 10V versions, sometimes failing short causing more damage to other components and ICs and also causing damage to the PCBs from leaking electrolyte so I decided to change out all of those purple electrolytics.
20180810_152535 by Alan Towell, on Flickr
For the general purpose caps I used Panasonic FC , for the audio boards I use Elna silmic, Nichicon Muze KZ and Fine gold and where there was Bipolar I use Nichicon ES, all purchased from Mouser
There was some values of electrolytic caps of less than 1UF so I replaced them with all film types.
Tantalum caps (only a couple in the machine) were all replaced with Electrolytics
On the audio board I replaced all ceramic films for COG or film types.
All replacement caps had a minimum voltage rating of 25V
There is a bit of work in this machine stripping it out and there are wires everywhere so it pays to take photographs when you are dismantling.
IMG_1916 by Alan Towell, on Flickr
IMG_1894 by Alan Towell, on Flickr
20180730_212943 by Alan Towell, on Flickr
Like a lot of old kit it was very dusty inside so a good dusting with my air line and paint brush go the majority off, a little Isopropanol on a soft brush did the rest (be careful with Isopropanol on film caps)
[url=https://flic.kr/p/29ZGUhh]
IMG_1900 by Alan Towell, on Flickrhttps://flic.kr/p/29ZGUhh[/URL]
Whilst it was stripped right down I serviced the 3 tape tension bellows which have a little silicone washer that can get leaky, also the rubber bellows themselves felt quite dried out so I cleaned them with platen clean rubber cleaner and rejuvenator and they are all working fine now. These bellows are a very fiddly job even with the deck stripped down.
IMG_1940 by Alan Towell, on Flickr
Also removed the reel motors and cleaned the brake hubs and pads, the bearings feel good so nothing else to do there.
I removed the huge capstan motor and cleaned the shaft, again the bearings feel perfect so left well alone.
I lubricated all of the tape tension linkage.
I cleaned all of the pots and switches with Caig deoxit D5 moving them multiple times back and forth
I removed every circuit board and recapped it as above and inspected all for dry soldered joints and reflowed where suspect.
Found some bad corrosion on the main control board and Capstan control board where pieces of foam are used to support the board from the cross bar
I treated it with some solder flux and then scraped away the mask
Fortunately the tracks were not to badly damaged so I tinned the tracks and re-flowed all of the IC connections.
IMG_1901 by Alan Towell, on Flickr
IMG_1903 by Alan Towell, on Flickr
IMG_1906 by Alan Towell, on Flickr
I re seated the Transistors in the power supply with new mica washers and heat sink compound and upgrade the 3 main power supply caps from 2200uf to 3300uf 50V.
I was advised on Tapheads.net to carry out a mod to the line amplifier which is said to give an improvement in distortion more than 30db as advised by Alex Nikitin from http://www.ant-audio.co.uk/index.php?cat=post&qry=Modifications
So I implemented that whilst I was in there
IMG_1915 by Alan Towell, on Flickr
My model has a Record Playback on the 2 track heads and playback only on the 4 track heads so very versatile
These are a beautiful R2R with a unique tape handling transport
http://www.thevintageknob.org/technics-RS-1500U.html
The speed stability and W&F are excellent due to the quarts Phase locked DD capstan drive motor with twin Capstan Roller tape drive.
Being manufactured from 1976 to 1981 they really were quite advance for their time but show their age with the simple belt driven counter
IMG_1948 by Alan Towell, on FlickrSo as some of these decks are over 40 years old they have started to suffer from Capacitor failure, particularly the 10V versions, sometimes failing short causing more damage to other components and ICs and also causing damage to the PCBs from leaking electrolyte so I decided to change out all of those purple electrolytics.
20180810_152535 by Alan Towell, on FlickrFor the general purpose caps I used Panasonic FC , for the audio boards I use Elna silmic, Nichicon Muze KZ and Fine gold and where there was Bipolar I use Nichicon ES, all purchased from Mouser
There was some values of electrolytic caps of less than 1UF so I replaced them with all film types.
Tantalum caps (only a couple in the machine) were all replaced with Electrolytics
On the audio board I replaced all ceramic films for COG or film types.
All replacement caps had a minimum voltage rating of 25V
There is a bit of work in this machine stripping it out and there are wires everywhere so it pays to take photographs when you are dismantling.
IMG_1916 by Alan Towell, on FlickrIMG_1894 by Alan Towell, on Flickr20180730_212943 by Alan Towell, on FlickrLike a lot of old kit it was very dusty inside so a good dusting with my air line and paint brush go the majority off, a little Isopropanol on a soft brush did the rest (be careful with Isopropanol on film caps)
[url=https://flic.kr/p/29ZGUhh]
IMG_1900 by Alan Towell, on Flickrhttps://flic.kr/p/29ZGUhh[/URL]Whilst it was stripped right down I serviced the 3 tape tension bellows which have a little silicone washer that can get leaky, also the rubber bellows themselves felt quite dried out so I cleaned them with platen clean rubber cleaner and rejuvenator and they are all working fine now. These bellows are a very fiddly job even with the deck stripped down.
IMG_1940 by Alan Towell, on FlickrAlso removed the reel motors and cleaned the brake hubs and pads, the bearings feel good so nothing else to do there.
I removed the huge capstan motor and cleaned the shaft, again the bearings feel perfect so left well alone.
I lubricated all of the tape tension linkage.
I cleaned all of the pots and switches with Caig deoxit D5 moving them multiple times back and forth
I removed every circuit board and recapped it as above and inspected all for dry soldered joints and reflowed where suspect.
Found some bad corrosion on the main control board and Capstan control board where pieces of foam are used to support the board from the cross bar
I treated it with some solder flux and then scraped away the mask
Fortunately the tracks were not to badly damaged so I tinned the tracks and re-flowed all of the IC connections.
IMG_1901 by Alan Towell, on FlickrIMG_1903 by Alan Towell, on FlickrIMG_1906 by Alan Towell, on FlickrI re seated the Transistors in the power supply with new mica washers and heat sink compound and upgrade the 3 main power supply caps from 2200uf to 3300uf 50V.
I was advised on Tapheads.net to carry out a mod to the line amplifier which is said to give an improvement in distortion more than 30db as advised by Alex Nikitin from http://www.ant-audio.co.uk/index.php?cat=post&qry=Modifications
So I implemented that whilst I was in there
IMG_1915 by Alan Towell, on Flickr
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