[Boards: 3 / a / aco / adv / an / asp / b / bant / biz / c / can / cgl / ck / cm / co / cock / d / diy / e / fa / fap / fit / fitlit / g / gd / gif / h / hc / his / hm / hr / i / ic / int / jp / k / lgbt / lit / m / mlp / mlpol / mo / mtv / mu / n / news / o / out / outsoc / p / po / pol / qa / qst / r / r9k / s / s4s / sci / soc / sp / spa / t / tg / toy / trash / trv / tv / u / v / vg / vint / vip / vp / vr / w / wg / wsg / wsr / x / y ] [Search | Extra juicy! | Home]

Restoration

This is a blue board which means that it's for everybody (Safe For Work content only). If you see any adult content, please report it.

Thread replies: 28
Thread images: 16

I have this old radio with a vinyl player (turntable, pickup) module. It's from the 70s. I want to make it work again. The pickup module is working I lubricated the motor and you can hear sound from the cartridge (the thing with the needle that reads from disk) when a disk is played. I resoldered some detached joints on this board but it still doesn't manage to pick up the signal from the vinyl player and play it through the speaker. I would love to make the radio work too. So what else should I be looking for on this board? Also I checked some capacitors (the big ones and some other small ones) with an ohm meter and they seem fine.
>>
>>1240884
>>
>>1240885
>>
>>1240887
>>
>>1240888
>>
>>1240891
>>
File: schematic-01.jpg (615KB, 2339x1586px) Image search: [iqdb] [SauceNao] [Google]
schematic-01.jpg
615KB, 2339x1586px
>>1240892
>>
File: schematic-1-01.jpg (556KB, 2339x1579px) Image search: [iqdb] [SauceNao] [Google]
schematic-1-01.jpg
556KB, 2339x1579px
>>1240896
>>
>>1240884

that might be 70s, but looks more like 60s to me. 70s was the era of modular components, meaning nobody packaged the turntable in a box with the tuner and amp, plus brushed aluminum and other metals had replaced wood cabinets for the most part.

so, if it is 70s, it's some weird crap that nobody wanted because the design would have been hopelessly dated. On the other hand, that was probably a cool possession in 1965.
>>
Should I start replacing components? I'm seriously thinking of replacing every single one I really want to make this work.
>>
>>1240915
Did you check any of the transistors?
>>
>>1240955
No. Brb
>>
>>1240892

This was soldered by an ape.
>>
>>1240977

apes can do better than that.
>>
>>1240977
>>1240981
Ikr? Though the close up that you made are just mounting points for a piece of metal for the switches.
I'm leaving the transistor check for tommorow. I only have an Analog multimeter with no probes just stripped wire and it's really sketchy. I don't know if the transistors are bad or there isn't a proper connection between the wire and leg.
>>
Update:
Talked with my grandfather, said the volume potentiometer is broken. Indeed it was, went to buy one.

Forgot check for power. The transformer was powering the turntable but the board has inputs from the transformer and from a bridge rectifier. Checked the outputs for the rectifier and I get none.
One thing though. Do you guys know what kind of potentiometer is this? The guy at the shop couldn't help me (I got a normal 3 pin one). He checked it and said the the weird pins make contact only when the knob is right in that position. Where could I find something like this? How can I manage without one?
>>
>>1242739
>>
File: schematic-01-01.jpg (215KB, 702x1157px) Image search: [iqdb] [SauceNao] [Google]
schematic-01-01.jpg
215KB, 702x1157px
>>1242740
Here's the potentiometer in the schematic. The red one is the 5 (or 6) pin one and the blue is a normal potentiometer. In the pictures with the board the volume potentiometer is the first one. You can see it has a black and yellow wire attached to 4th and 5th pin. The 6th pin is in the back cover of potentiometer and is not connected to anything.
>>
>>1242742
Fuck
>>
>>1242743
Here's the cover
>>
>>1242739
>Do you guys know what kind of potentiometer is this?
I've seen pots with one tap before.
The tap and associated components were to effect a 'loudness' function to the volume control.
The idea is to boost bass at lower volume settings.
This is probably a variation of that.
It would probably function with the wires to the taps left unconnected.
That said, it may sound 'funny' without the proper pot.
>>
>>1242756
I was thinking of connecting a switches between the said wires and the pot's leg (have to find out which is which).
>>
>>1242739
This is P301, the volume potentiometer, 250Klin (linear) with two taps for the 'loudness' network connected to them. The purpose of this network is to boost bass and treble at low volumes.

This type of potentiometer may be difficult to obtain unless salvaged from another old radio. The loudness correction is not essential though and you could replace it with a 250Klog (logarithmic) potentiometer which is readily available. 220Klog would work as well.

The traces left by the slider on the carbon film tell you that this radio was mostly operated at low volume, rarely at medium and never at full power, which is totally understandable given the awkward distortions the germanium transistor power amp would have greeted you with.

The excellent circuit diagram is full of testable voltages in case you need to repair that part. The (blue) bridge rectifier seems to be a selenium type which tend to age and degrade. It can be replaced with a (comparably tiny) silicon bridge or with four 1N400X diodes if need be. The 80mA fuse may also need an inspection. The record player seems to be independent with no connection to the transformer. It may be connected to one of the two DIN jacks at the back (the other being for a tape recorder) unless there's already an internal connection.

Regarding your multimeter, maybe it's time to invest 10€ or so for a cheap digital meter with at least 1MΩ input resistance? That would be extremely convenient should some faulty component need to be identified. I'm familiar with the circuitry and may be able to offer my assistance if required.
>>
>>1242739
>Where could I find something like this?
Buy a 'regular' pot of the same physical size.
Disassemble
Swap out wafers
Reassemble
You now have a 'new' correct pot.
>>
Sorry for not replying had to do some work on my car.
>>1242840
Thx for standing by. I got myself a decent multimeter, checked the transformer and has no output :p so the board is completely out of power. The turntable was working because it was getting current directly from the outlet. It bypassed the transformer. I'm gonna get a new transformer then start troubleshooting the real problems.
>>1242861
Can't do that unfortunately, the old pot is way bigger compared to these new ones and I lost the spinning thing that made contact on the wafer.
>>
>>1243579
Oh and the fuses are ok.
>>
>>1243579
>checked the transformer and has no output
Check the resistance on the primary.
Some transformers had a fuse embedded under the paper/tape for the primary.
If the primary is open you may be able to peel away the covering enough to gain access to the 'fuse' under it.
Jumper the fuse and the transformer works again.

Run other tests right away to figure out why the fuse (if there is one) burned out.
>>
>>1243708
BIG NEWS, ITS WORKING HOLY SHIT
The transformer was ok. I pulled it out of the enclosure and tested it again. It displayed correct output, 6,5v and 16v. So then proceeded to replace the bridge rectifier with the new one. It outputs 20,5 volts. Then checked a few capacitor and diode voltages and they seemed fine. Then checked the speaker output voltage and it had some. So I connected the speaker and the turntable to the board and VOILA it's working really great. Even the radio is working. I could catch some weird stations on long waves on the board antenna. I'm sorry about that unique potentiometer. Maybe it was still usable even in that state. Can't I connect the filter wire to the pots leg with a switch between? Then flip the switch when the pot is at 40% let's say?
Also this board is dirty and smells like hell. I sprayed it with isopropyl alcohol with a syringe then blowed it with air duster but it still looks and smells like garbage juice. Should I repeat the process but with distilled water? I was also thinking of using a very soft brush on it.
>Pic related: the old bridge rectifier. It's a heatsink and a rectifier at the same time.
Thread posts: 28
Thread images: 16


[Boards: 3 / a / aco / adv / an / asp / b / bant / biz / c / can / cgl / ck / cm / co / cock / d / diy / e / fa / fap / fit / fitlit / g / gd / gif / h / hc / his / hm / hr / i / ic / int / jp / k / lgbt / lit / m / mlp / mlpol / mo / mtv / mu / n / news / o / out / outsoc / p / po / pol / qa / qst / r / r9k / s / s4s / sci / soc / sp / spa / t / tg / toy / trash / trv / tv / u / v / vg / vint / vip / vp / vr / w / wg / wsg / wsr / x / y] [Search | Top | Home]
Please support this website by donating Bitcoins to 16mKtbZiwW52BLkibtCr8jUg2KVUMTxVQ5
If a post contains copyrighted or illegal content, please click on that post's [Report] button and fill out a post removal request
All trademarks and copyrights on this page are owned by their respective parties. Images uploaded are the responsibility of the Poster. Comments are owned by the Poster.
This is a 4chan archive - all of the content originated from that site. This means that 4Archive shows an archive of their content. If you need information for a Poster - contact them.