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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 18th Jan 2021, 9:15 pm   #21
Ted Kendall
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Default Re: Akai 1800 Check Out

More to the point, I don't suppose they would expect them to be in use beyond a decade later.
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Old 18th Jan 2021, 9:27 pm   #22
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Default Re: Akai 1800 Check Out

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Originally Posted by Ted Kendall View Post
More to the point, I don't suppose they would expect them to be in use beyond a decade later.
I would have hoped that they would have expected them to still be in use and functional beyond a decade later but I do get your point.

David
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Old 18th Jan 2021, 10:29 pm   #23
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Default Re: Akai 1800 Check Out

In photo 1 there is a solid core silver coloured wire (Steel I think) on the left hand side middle level going across from the front to the rear of the wooden case.

Photo 2 shows the wire going into the case wood at the front. It looks like the wire might make contact with the brass threaded insert just below where the wire enters the case, but by meter measurement there is no contact. This insert is for one of the tape deck securing screws to screw into. It does look like the silver coloured metal bracket will press against/make contact with the wire when the tape deck is fitted and the metalwork of the tape deck also will be at same potential. When the amplifier chassis is fitted it will make contact with the bottom part of the bracket so the chassis then will be also at same potential which will connect back to the power supply ground, there is no external earth connection (2 core mains flex) but there will be soon.

Photo 3 shows the other end of the wire going into the wood at the rear of the case and sitting a little proud.

Photo 4 shows the black painted metal cover that fits on the rear of the case, the part of the cover that would sit on top of the wire and make contact is copper coloured (looks more yellow in the photo due to flash).

Occasionally have seen similar on other recorders and have never fully understood the function of the wire.

Now it seems just a grounding/earthing connection method but why not have proper hardwired ground wire connections ?

David
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Old 19th Jan 2021, 5:11 pm   #24
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Default Re: Akai 1800 Check Out

Been cleaning the amplifier chassis of quite a lot of sticky dust deposits and generally checking it out. It has 5 x NEC 81 valves, not sure what 81 means, if the year then not original valves. On some of the valves the valve type number is rubbed off, so need to check the connections to the valve bases to work out what those valves are/should be .

One of the valves a 6AR5, had several cracks in top of the glass envelope, removing the valve to check its number, resulted in the glass breaking, so now looking for a 6AR5 or similar.

No obvious sign of any paper/waxy capacitors, but I think many of the capacitors that connect to the valves are on 2 little boards that are mounted with the components downmost so not yet seen underneath them.

There are another 2 little boards where the left and right PB/Record slide switches are mounted, these boards are heavily encased by metalwork but can just see that there are transistors on these boards. Due to the way they are positioned and wired, looks just about impossible to access their components so hopefully no live monitoring will be required on these boards.

So the original research which indicated the 1800 was all valve (not including the 8 track unit) like the 1700, was incorrect, the 1800 is a hybrid mixture of valves and transistors, even ignoring the 8 track unit.

I purchased/downloaded a SAMs Photofact manual which covers the 1700, 1710 and 1800, this manual is a bit of a hotchpotch with various pages taken from different manuals. It has the schematic for the 8 track unit but the main schematic just shows valves so is either 1700 or 1710. So the only schematic that I have seen so far that so shows transistors and valves is the 1800L but very difficult to read.

The 1800L evidently has leather covered case.
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Last edited by DMcMahon; 19th Jan 2021 at 5:19 pm. Reason: Typo corrections
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Old 19th Jan 2021, 5:42 pm   #25
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Default Re: Akai 1800 Check Out

Looks like the Roberts 1725-8L III schematic (which is reasonably legible) will be the closest schematic, this shows the valves and the transistors plus the 8 track circuitry.

The Roberts 1725-8L is virtually a rebadged/clone of the Akai 1800/1800L, there being 3 variants the 1725-8L, the 1725-8L II & the 1725-8L III, no idea what the subtle differences are.

Even though effectively largely a clone, there are some differences, it is 3 speed with electric control, the 1800 is 2 speed with mechanical control, not sure about the 1800L.
Some of the front panel controls are different, position/layout wise.
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Old 20th Jan 2021, 10:54 am   #26
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Default Re: Akai 1800 Check Out

Looks like the Roberts 1725-8L has the 8 track unit mounted in correct/normal orientation and in the Roberts 1725-8L III the 8 track is the same as the 1800 with it being mounted on its side.
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Old 20th Jan 2021, 12:25 pm   #27
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Default Re: Akai 1800 Check Out

Been checking some of the amplifier (valve section) wiring/connections comparing to schematics.

The 1700 schematic even though similar has different valves and often different component values. The 1800L schematic looks to be very close to my 1800 but not easy to read the out of focus yellow schematic, printing it A3 size helps a fraction.
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Old 20th Jan 2021, 8:30 pm   #28
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Default Re: Akai 1800 Check Out

Fitted 3 core mains cable + 3 pin plug to replace the twin flex and earthed the metalwork.

Checked the mains transformer windings resistances:-

Primary 0V to 240V = 24.4 Ohm
Secondary 250V to 250V = 228 Ohm
Secondary 19V to 0V = 9.2 Ohm
Secondary 0V to 250V = 112 Ohm
Secondary 19V to 250V = 107 Ohm
Secondary 6.3V 2A = 0.2 Ohm
Secondary 6.3V 1A = 0.2 Ohm
Secondary 6.3V 2A = 0.2 Ohm

With valves removed measured the mains transformer secondary output voltages:-

Secondary 250V to 250V = 546 VAC
Secondary 19V to 0V = 24.04 VAC
Secondary 6.3V 2A = 6.9 VAC
Secondary 6.3V 1A = 6.9 VAC

From the schematic identified which of the 4 large electrolytics (one is dual can) is which HT voltage, in preparation for checking the various HT voltages later.

Tried to have a quick look at the components on the underside of the 2 boards in first attachment, the right hand side one is possible with some difficulty to get/see underneath, the left hand board is impossible to see underneath due to the short length of some of the connecting wires that connect to the valves. For any live monitoring on this board would have to make some longer connection leads, to be able to identify what components are what and where.

Cleaned up somewhat the tape deck. Got inside the 8 track to clean the heads etc. Quite a bit of rusting on the plated metalwork, managed to remove some of it.

Manually operating the head lift mechanism and the program selector it is all quite stiff due to being gummed up/dried grease. Trying to strip it down further to clean and lubricate, but cannot get the heads assembly high enough to come off the shaft due to the heads cables being too tight, will have to unsolder all the wires from the heads.

No sign of a end of tape (foil) sensor/contacts for the automatic program/track changeover, did early 8 tracks not have this feature ?
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Old 20th Jan 2021, 9:58 pm   #29
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Default Re: Akai 1800 Check Out

There were some 8-track players that did not have auto track-change facilities, but these were mostly cheap and chearful portable units. All machines capable of recording had auto-change. It looks a little different on these Akai units becuase the erase head itself forms one of the two contacts that get shorted out when the foil comes along. The other contact is the tape guide that is on the left side of the erase head (furthest from the rec/play head).

Just noticed that it's the guide on the right in your photo.
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Old 20th Jan 2021, 11:35 pm   #30
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Default Re: Akai 1800 Check Out

Thank you, that is good to know. I thought it would be strange for a recorder of reasonable quality not to have the auto track change facility. I have been trying to see it on the schematic but such poor quality cannot make it out.

When I power up the tape deck I will check it out.

David
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Old 21st Jan 2021, 12:52 am   #31
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Default Re: Akai 1800 Check Out

Section from Roberts 1725 8-L III schematic which should be basically the same as the Akai 1800, shows the circuit. It must be the "Contact SW" lines, nothing obvious from that, that one of the contact points is the erase head.

Tomorrow when I strip apart the head lift assembly and selector mechanism , I will check out the wring connections fully and then all will be clear.
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Old 21st Jan 2021, 5:58 pm   #32
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Default Re: Akai 1800 Check Out

Head assembly stripped out, cannot remove (despite lots of trying) the track change selector mechanism so have cleaned in-situ and will lubricate in-situ.

Not 100% checked yet, but can see no sign of the auto track change sensor contact being part of the erase head.
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Old 21st Jan 2021, 10:26 pm   #33
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Default Re: Akai 1800 Check Out

Quote:
Originally Posted by DMcMahon View Post
Yes Ted that was a silly statement of mine, I was referring to the R2R (not including the 8 track) itself being all valves, the 8 track of course will be solid state so you are totally correct, the unit as a whole is hybrid.

David
From other checks on the 8 track player/recorder can now see there are no transistors in it. The heads connect directly back to the transistors in the pre-amplifier section of the amplifier chassis.

The SAMs Photobook manual I have for 1700, 1710 and 1800 does show transistors on the 8 track schematic, this schematic must be for the 1800 as I believe that the 1700 and 1710 do not have an 8 track unit fitted. The schematic and part list in the SAMs manual indicates a totally different 8 track unit, in addition to the transistors, it also has its own power supply and its own motor etc (my 1800 shares the main capstan motor shaft for use with the 8 track)

As the SAMs is a USA manual then maybe the 1800 that was distributed in the USA had a different 8 track unit or maybe the SAMs manual reflects a later version model of the 1800.
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Old 22nd Jan 2021, 12:03 am   #34
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Default Re: Akai 1800 Check Out

Can now see how auto track change contacts work.

The tape guide to the right of the erase head is insulated from the metalwork by a little pad that sits between the base of the tape guide and the metalwork it is secured to, can be just seen in third photo in Post 32. The securing screws of the tape guide connect to a track on the 8 track board which in turn connects to the low side of the track change solenoid.

The tape guide to the left of the erase head is screwed straight to the metalwork.

So when the tape foil bridges the above 2 tape guides it takes the low side of the track change solenoid down to ground which energises the solenoid, which changes the track/program.

The tape cut out on the left hand tape guide is quite a bit deeper than the right tape guide and also deeper than the tape cut outs on the Play/Record head tape guides, must be a good reason for this.
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Old 23rd Jan 2021, 11:01 am   #35
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Default Re: Akai 1800 Check Out

Cleaned, lubricated and re-assembled the 8 track head assembly and track change selector assembly, manually operating the solenoid the track change assembly is now working well.

Cleaned the heads in the tape deck chassis and generally cleaned the rest of the chassis.

Manually operated the speed change mechanism which was quite stiff, after a few operations it stopped working and could see that a little plastic tapered pin had either broken or come out of part of the mechanism. The pin engages in vertical slot on the capstan shaft and moves a sleeve up and down the capstan shaft. Removed the parts for cleaning, lubrication and pin repair.

Connected the tape deck chassis to the amplifier chassis and powered up OK. Looks difficult to access areas for any fault finding.

Motor runs and capstan shaft rotates OK (a bit noisy). With no tape loaded, rewind (RWD) and fast forward (FFD) work well, tape counter works. FFD & RWD selector is stiff in operation. In my experience this is fairly normal (with similar Akai's) due the various mechanisms particularly the FFD/RWD selector shaft detent assembly, but I will strip, clean and lubricate the associated parts to see if any better. The RWD/FFD operating cam looks to be in good condition and do not want too much stress on it due to overly stiff mechanism.

Play not checked yet as still to rebuild the Play/Record selector with donor cam and associated bits.

8 track auto change selector not working reliably when manually operated from switch (annoying as working so well when manually operated) and none of the 4 track indicator lamps are lighting up (lamps look OK).
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Old 24th Jan 2021, 10:48 am   #36
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Default Re: Akai 1800 Check Out

Stripped the FFD/RWD selector, as expected the main stiffness is the selector shaft & detent assembly mechanism, will try and get it eased a little with lubrication. The Play mechanism with same type steel ball detent mechanism (but different shaft length), by comparison is relatively easy to turn

Both remaining cams on this assembly are in good condition.
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Old 24th Jan 2021, 3:42 pm   #37
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Default Re: Akai 1800 Check Out

The damage caused to the case (Post 15) where the top 2 rubber feet had been knocked hard at some time was pretty bad, so have glued wood blocks over the damaged areas to tidy/strengthen the case. Will use wood filler in the large holes on the other side of the blocks.

Probably will not be able to refit the original large feet in same position as they have shortish stud fixing, so will either relocate the feet or use different feet secured to the new blocks.
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Old 26th Jan 2021, 11:08 pm   #38
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Default Re: Akai 1800 Check Out

Severe stiffness of the FFD/RWD selector improved a lot with oiling its shaft and greasing the detents.

Re-assembled the complete FFD/RWD selector and Play/Record selector, both working well. So the donor top cam on the Play/Record selector is good. The donor lower cam on the Play/Record selector (which actuates the PB/Record switches to the Record position via flexible linkage probably will be no good (as is), will look at this aspect further later.

For good measure stripped, cleaned and lubricated all the numerous tape transport mechanisms on the top panel, quite a jigsaw getting them all back correctly.

Presently trying to get the tape speed change mechanical mechanism to work correctly, it is sprung loaded and when speed manually changed the capstan shaft speed sleeve should pop up or down to the required position.
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Old 27th Jan 2021, 3:33 pm   #39
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Default Re: Akai 1800 Check Out

Quote:
Originally Posted by DMcMahon View Post
8 track auto change selector not working reliably when manually operated from switch (annoying as working so well when manually operated) and none of the 4 track indicator lamps are lighting up (lamps look OK).
Checked the 4 track indicator lamps OK and associated wiring back to the 18 way edge connector J9 at the amplifier chassis. This J9 connector is on a cable assembly that fits onto the edge contacts (designated as P709 on the schematic) of the 8 track board.

Looking at the schematic see that the track indicator lamp 6.3 VAC voltage supply is switched through to the lamps (via the track selector switch) by the cartridge inserted microswitch. In a normal stand alone 8 track unit the cartridge inserted microswitch switches mains power for the motor/mains transformer.

On previous testing did not have a tape cartridge inserted so tried again with tape cartridge fitted but still no track lamps lighting up. So need to verify that the 6.3V is reaching the microswitch and is being switched through.
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Old 27th Jan 2021, 11:21 pm   #40
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Default Re: Akai 1800 Check Out

Got the tape speed change parts working properly.

The left hand tape guide on the head block was very loose so had to tighten down its securing nut. To reach this easier I removed the tape counter for better access. Found the tape counter metalwork is same cast material as the selector cams and is not in great condition.

Fitted a tape to test the tape transport and first new problem encountered is that the motor no longer starts up, it needs a helping hand to get it going, it has never done this before.

Then was totally amazed that everything is trying to go in reverse, Play, Rewind and Fast Forward with result lots of slack tape. Fairly sure that on previous checks (with no tape) that everything was going in correct direction.

Unless I am going stupid it appears that the motor is rotating in the wrong direction, somewhat disbelieving myself but it definitely appears to be what is happening

Will have a fresh look tomorrow.
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